Download 1 Marsbugs: The Electronic Astrobiology Newsletter, Volume 12

Marsbugs: The Electronic Astrobiology Newsletter
Volume 12, Number 11, 30 March 2005
Editor/Publisher: David J. Thomas, Ph.D., Science Division, Lyon College,
Batesville, Arkansas 72503-2317, USA. [email protected]
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Articles and News
Page 1
COMPARING THE TRIAD OF GREAT MOONS
By Jonathan Lunine
Page 2
NASA'S SPITZER MARKS BEGINNING OF NEW AGE OF
PLANETARY SCIENCE
NASA/JPL release 2005-050
Page 3
PUSHING THE PLANETARY ENVELOPE (INTERVIEW
WITH NEIL DEGRASSE TYSON, PART 5)
By Leslie Mullen
Page 5
MYSTERY MINERALS FORMED IN FIREBALL FROM
COLLIDING ASTEROID THAT DESTROYED THE
DINOSAURS
University of Chicago release
Page 6
NEW FRONTIER OPENS IN THE SEARCH FOR LIFE ON
OTHER PLANETS
NASA/GSFC release
Page 7
CENSORSHIP OF IMAX FILMS THREATENS INTEGRITY
OF SCIENCE, LEADER SAYS
From LiveScience
Page 7
CROSSING THE TREELINE
By Chris McKay
Page 7
CLIMATE MODELS REVEAL INEVITABILITY OF
GLOBAL WARMING
By Sarah Graham
Page 7
ON AMMONIA AND ASTROBIOLOGY
By Jonathan Lunine
Mission Reports
Page 8
CASSINI SIGNIFICANT EVENTS FOR 10-16 MARCH 2005
NASA/JPL release
Page 10
DEEP IMPACT MISSION STATUS REPORT
NASA release 05-086
Page 11
MARS EXPRESS: THE MEDUSA FOSSAE FORMATION
ON MARS
ESA release
Page 12
MARS GLOBAL SURVEYOR IMAGES
NASA/JPL/MSSS release
Page 12
MARS ODYSSEY THEMIS IMAGES
NASA/JPL/ASU release
COMPARING THE TRIAD OF GREAT MOONS
By Jonathan Lunine
From Astrobiology Magazine
Jonathan Lunine, a professor of planetary science and physics at the
University of Arizona's Lunar and Planetary Laboratory in Tucson, Arizona,
is also an interdisciplinary scientist on the Cassini/Huygens mission. Lunine
presented a lecture entitled "Titan: A Personal View after Cassini's first six
months in Saturn orbit" at a NASA Director's Seminar on January 24, 2005.
This edited transcript of the Director's Seminar is Part 3 of a 4-part series.
Left: High resolution close-up of Io's volcanic
surface. Only a third the size of Earth and five
times as far from the Sun, Io generates twice our
total terrestrial heat bill.
Image credit:
NASA/Galileo. Right: Titan continues to puzzle
scientists who speculate about the hydrocarbon
rich composition. Image credit: NASA/JPL.
Saturn's moon Titan is one of a triad of giant moons, the other two being
Jupiter's moons Ganymede and Callisto. Interestingly, these moons all have
about the same density, and therefore about the same mass and radius. The
density for these three objects is between 1.8 and 1.9 grams per cubic
centimeter, and the radius is between 2500 and 2600 kilometers. This makes
them the three largest moons in the solar system—much larger than our own
moon and larger than the planet Mercury. Because they are the same density
and size, they are also composed of the same materials.
Presumably, there must be some process that truncates the formation or
growth of satellites at about the size of Ganymede, Callisto, and Titan. It's not
clear what that process is, but one clue can be found in the density—you're
making these bodies out of rock and ice. When you get to the size of Titan,
the energy that's released during formation, just due to the infall of material, is
about equal to the latent heat per gram of the ice-component of the material.
In other words, the energy released toward the end of accretion is equal to the
heat needed to vaporize water ice. That means that if water ice is the stuff
you're accreting, you're vaporizing it and it's going away, so accretion
becomes less efficient. Maybe that's a natural truncation process for these
rocky and icy worlds around the giant planets.
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
2
But if you add ammonia to any of these objects—Ganymede, Callisto or
Titan—there would be an ice mantle with a liquid layer within it, due to the
ammonia lowering the melting point for the water ice. That liquid layer is
sandwiched between the lower density ice and the higher density, high
pressure ice phases. Yet the environment where Ganymede and Callisto
formed was simply too warm for substantial amounts of ammonia to bond
with the water ice. You need a certain temperature to get ammonia hydrates
forming in these planetisimals, and I think it was just too warm at Jupiter.
If ammonia is present on Titan, it could be the source of the nitrogen in the
atmosphere, since ammonia is the bearer of nitrogen. With a liquid layer, the
ammonia also would allow for what's called cryovolcanism, and therefore
bleed some material onto the surface. Having a moon that's volatile-rich in
this way leads naturally to the occurrence of an atmosphere.
Read the original article at http://www.astrobio.net/news/article1493.html.
NASA'S SPITZER MARKS BEGINNING OF NEW AGE OF
PLANETARY SCIENCE
NASA/JPL release 2005-050
22 March 2005
This image shows a possible caldera from which liquid water or slush
may have once flowed on Ganymede. Image credit: NASA/JPL.
What sets Titan apart from Ganymede and Callisto, however, is the presence
of an atmosphere. This atmosphere was discovered in 1943, when Gerard
Kuiper detected Titan's methane using an Earth-based telescope. Voyager 1
discovered molecular nitrogen as the dominant constituent of Titan's
atmosphere in 1980. That was done indirectly, by using an ultraviolet
spectrometer to get the density of the atmosphere, and then putting that
information together with data from an infrared spectrometer. From those
instruments together, it was clear that nitrogen was the dominant constituent
of the atmosphere. We don't have to worry about that indirectness anymore,
because the Cassini orbiter mass spectrometer and the Huygens gas
chromatograph mass spectrometer have both directly detected—or tasted, if
you want to think of it that way—nitrogen as the dominant constituent of
Titan's atmosphere. They also directly detected methane. So that era of
spectroscopy and inference has now drawn to a close because of Cassini.
NASA's Spitzer Space Telescope has for the first time captured the light from
two known planets orbiting stars other than our Sun. The findings mark the
beginning of a new age of planetary science, in which "extrasolar" planets can
be directly measured and compared.
Because methane is abundant in Titan's atmosphere, it becomes a very
interesting place from the point of view of organic chemistry. Its atmosphere
is between 2 and 4 percent methane—going from the middle, coldest part of
the atmosphere, the tropopause, down to the surface. And that means there is
abundant organic chemistry going on, powered primarily in the upper
atmosphere by ultraviolet light from the sun. There may be additional
chemistry occurring on the surface, powered by other energy sources.
The temperature at the surface of Titan is 95 degrees Kelvin, and the
temperature drops off with altitude to a temperature of 70 Kelvin at about 40
kilometers. Titan has a much more distended atmosphere than the Earth's
because of the lower gravity. The surface pressure on Titan is one and a half
bars, so the density of Titan's atmosphere at the surface is four times denser
than the air at sea level on the Earth. This is the second densest atmosphere
on the four solid bodies with substantial atmospheres in the solar system,
second only to Venus. Earth then is third, and Mars is fourth.
So why does Titan have an atmosphere, when Ganymede and Callisto do not?
I think the answer is becoming abundantly clear from the Cassini data. Titan
has accreted, or acquired, large amounts of ammonia in addition to the water.
Large, meaning maybe a few percent, but that's enough.
We know a fair amount about the interiors of Ganymede and Callisto from the
Galileo orbiter that made multiple flybys of the moons of Jupiter from 1995
onward to 2003. Ganymede is highly differentiated—the silicates and the
metal are not simply mixed together, it appears that they're actually separated
out. That implies fairly highly temperatures during accretion. Ganymede has
a silicate mantle around a metal core, then an ice mantle as well, with highpressure ice phases. Above about 2 kilobars, water ice assumes different
structures that are denser than liquid water.
Now, that's important, because on a moon that has some melting, the liquid
water layer is going to be sandwiched between ice layers of different
pressures. It doesn't appear that there's such a liquid layer within Ganymede
and Callisto, although there may have been some softening of the ice.
This graph of data from NASA's Spitzer Space telescope shows
changes in the infrared light output of two star-planet systems (one
above, one below) located hundreds of light-years away. The data
were taken while the planets, called HD 209458b and TrES-1,
disappeared behind their stars in what is called a "secondary eclipse".
The dip seen in the center of each graph represents the time when the
planets were eclipsed, and tells astronomers exactly how much light
they emit. Why a secondary eclipse? When a planet transits, or
passes in front of, its star, it partially blocks the light of the star. When
the planet swings around behind the star, the star completely blocks its
light. This drop in total light can be measured to determine the amount
of light coming from just the planet. Image credits: NASA/JPLCaltech/D. Charbonneau (Harvard-Smithsonian CfA) and NASA/JPLCaltech/D. Deming (Goddard Space Flight Center).
"Spitzer has provided us with a powerful new tool for learning about the
temperatures, atmospheres and orbits of planets hundreds of light-years from
Earth," said Dr. Drake Deming of NASA's Goddard Space Flight Center,
Greenbelt, MD, lead author of a new study on one of the planets.
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
"It's fantastic," said Dr. David Charbonneau of the Harvard-Smithsonian
Center for Astrophysics, Cambridge, MA, lead author of a separate study on a
different planet. "We've been hunting for this light for almost 10 years, ever
since extrasolar planets were first discovered." The Deming paper appears
today in Nature's online publication; the Charbonneau paper will be published
in an upcoming issue of the Astrophysical Journal.
So far, all confirmed extrasolar planets, including the two recently observed
by Spitzer, have been discovered indirectly, mainly by the "wobble" technique
and more recently, the "transit" technique. In the first method, a planet is
detected by the gravitational tug it exerts on its parent star, which makes the
star wobble. In the second, a planet's presence is inferred when it passes in
front of its star, causing the star to dim, or blink. Both strategies use visiblelight telescopes and indirectly reveal
In the new studies, Spitzer has directly observed the warm infrared glows of
two previously detected "hot Jupiter" planets, designated HD 209458b and
TrES-1. Hot Jupiters are extrasolar gas giants that zip closely around their
parent stars. From their toasty orbits, they soak up ample starlight and shine
brightly in infrared wavelengths.
3
The Spitzer data told the astronomers that both planets are at least a steaming
1,000 Kelvin (727 degrees Celsius, 1340 Fahrenheit). These measurements
confirm that hot Jupiters are indeed hot. Upcoming Spitzer observations using
a range of infrared wavelengths are expected to provide more information
about the planets' winds and atmospheric compositions.
The findings also reawaken a mystery that some astronomers had laid to rest.
Planet HD 209458b is unusually puffy, or large for its mass, which some
scientists thought was the result of an unseen planet's gravitational pull. If
this theory had been correct, HD 209458b would have a non-circular orbit.
Spitzer discovered that the planet does in fact follow a circular path. "We're
back to square one," said Dr. Sara Seager, Carnegie Institution of Washington,
Washington, co-author of the Deming paper. "For us theorists, that's fun."
Spitzer is ideally suited for studying extrasolar planets known to transit, or
cross, stars the size of our Sun out to distances of 500 light-years. Of the
seven known transiting planets, only the two mentioned here meet those
criteria. As more are discovered, Spitzer will be able to collect their light—a
bonus for the observatory, considering it was not originally designed to see
extrasolar planets. NASA's future Terrestrial Planet Finder coronagraph, set
to launch in 2016, will be able to directly image extrasolar planets.
Shortly after its discovery in 1999, HD 209458b became the first planet
detected via the transit method. That result came from two teams, one led by
Charbonneau. TrES-1 was found via the transit method in 2004 as part of the
NASA-funded Trans-Atlantic Exoplanet Survey, a ground-based telescope
program established in part by Charbonneau.
Artist's concepts and additional information about the Spitzer Space Telescope
are available at http://www.spitzer.caltech.edu/Media.
NASA's Jet Propulsion Laboratory, Pasadena, CA, manages the Spitzer Space
Telescope mission for NASA's Science Mission Directorate, Washington, DC.
Science operations are conducted at the Spitzer Science Center, at the
California Institute of Technology in Pasadena. Caltech manages JPL for
NASA. For more information contact Nancy Neal Jones, Goddard Space
Flight Center, 301/286-0039; or David Aguilar, Harvard-Smithsonian Center
for Astrophysics, 617/495-7462.
This artist's concept shows what a fiery hot star and its close-knit
planetary companion might look close up if viewed in visible (left) and
infrared light. In visible light, a star shines brilliantly, overwhelming the
little light that is reflected by its planet. In infrared, a star is less
blinding, and its planet perks up with a fiery glow. In this figure, the
colors represent real differences between the visible and infrared views
of the system. The visible panel shows what our eyes would see if we
could witness the system close up. The hot star is yellow because, like
our Sun, it is brightest in yellow wavelengths. The warm planet, on the
other hand, is brightest in infrared light, which we can't see. Instead,
we would see the glimmer of star light that the planet reflects. In the
infrared panel, the colors reflect what our eyes might see if we could
retune them to the invisible, infrared portion of the light spectrum. The
hot star is less bright in infrared light than in visible and appears
fainter. The warm planet peaks in infrared light, so is shown brighter.
Their hues represent relative differences in temperature. Because the
star is hotter than the planet, and because hotter objects give off more
blue light than red, the star is depicted in blue, and the planet, red.
The overall look of the planet is inspired by theoretical models of hot,
gas giant planets. These "hot Jupiters" are similar to Jupiter in
composition and mass, but are expected to look quite different at such
high temperatures. The models are courtesy of Drs. Curtis Cooper
and Adam Showman of the University of Arizona, Tucson. Image
credit: NASA/JPL-Caltech/R. Hurt (SSC).
To distinguish this planet glow from that of the fiery hot stars, the astronomers
used a simple trick. First, they used Spitzer to collect the total infrared light
from both the stars and planets. Then, when the planets dipped behind the
stars as part of their regular orbit, the astronomers measured the infrared light
coming from just the stars. This pinpointed exactly how much infrared light
belonged to the planets. "In visible light, the glare of the star completely
overwhelms the glimmer of light reflec star-planet contrast is more favorable
because the planet emits its own light."
Contacts:
Whitney Clavin
Jet Propulsion Laboratory, Pasadena, CA
Phone: 818-354-4673
Dolores Beasley
NASA Headquarters, Washington, DC
Phone: 202-358-1753
Additional articles on this subject are available at:
http://www.astrobio.net/news/article1496.html
http://cl.exct.net/?ffcd16-fe6115767c61067d7610-fe28167073670175701c72
http://www.space.com/scienceastronomy/030522_exoplanet_direct.html
http://www.spacedaily.com/news/extrasolar-05n.html
http://spaceflightnow.com/news/n0503/22exoplanets/
http://spaceflightnow.com/news/n0503/22exoplanets/index2.html
http://www.universetoday.com/am/publish/first_light_extrasolar.html
PUSHING THE PLANETARY ENVELOPE (INTERVIEW WITH NEIL
DEGRASSE TYSON, PART 5)
By Leslie Mullen
From Astrobiology Magazine
23 March 2005
Neil deGrasse Tyson is the Director of the Hayden Planetarium at the
American Museum of Natural History in New York, and also a Visiting
Research Scientist at Princeton University's Department of Astrophysics. He
writes a monthly column called "Universe" for Natural History magazine, and
is the author of several books, including One Universe: At Home in the
Cosmos and The Sky is Not the Limit: Adventures in an Urban Environment.
His most recent project is the NOVA four-part series, Origins. As host of the
PBS miniseries, Tyson guides viewers on a journey into the mysteries of the
universe and the origin of life itself.
In this interview with Astrobiology Magazine editor Leslie Mullen, Tyson
discusses his role in the President's Commission on the Moon, Mars and
Beyond, and explains what drives us to seek a future in space.
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
4
over the time necessary to get to Mars and beyond. And over the political and
economic fluctuations that have damned expensive projects in the past, like
the Supercollider, or the space station.
AM: Speaking of time, what sort of timeline do you foresee for the President's
goal?
NT: Thirty years. That's a lot of presidential elections, so this can't be a
partisan issue. Historically it's been non-partisan. It's been partisan on its
edges, but not at its core. Kennedy said, "Let's go to the moon," but it's
Nixon's signature that's on the moon. We all did this together.
AM: But thirty years for the moon, Mars, and beyond do you really think
we'll do it in that short of a time?
Cat's Eye Nebula. Image credit: ESA
Astrobiology Magazine (AM): You mentioned the Apollo program, which
was due in part to the Cold War.
Neil deGrasse Tyson (NT): We would have never gone to the moon without
the Cold War, I am certain of that.
AM: Do you think it's beneficial to the goal of exploration to have that kind of
competition with other nations, or do you foresee a future of cooperation with
space-faring nations such as China, Russia, Japan.
NT: I think that's a phased time with a modest budget. If you don't have much
money, then you stretch it out over a longer time in order to accomplish it. So
rather than telling Congress, "Why don't you triple NASA's budget so we can
do this in ten years?" We say we'll just up-tick the budget a little bit and we'll
do it in thirty. But meanwhile, we'll do other things on route so that we're
always pushing the envelope that hadn't been pushed before, or hasn't been
pushed in a very long time. And going into Low Earth Orbit is not one of
those envelopes.
AM: Yeah, the urgency behind that seems to have faded.
NT: For Low Earth Orbit? That's right. It's faded because it's not new. But
look at the excitement behind Spaceship One.
NT: I've spoken and written at length about this very subject. It has to do with
what drives civilizations to invest high levels of resources towards one project
or another.
If you look at the history of major funded projects, if you made a list of the
most expensive things cultures have ever undertaken, there are only three
drivers. One of three drivers accounts for every one of the most expensive
things people have ever done. And if you made that list you'd include things
like the Pyramids, the Great Wall of China, the Manhattan Project, etc.
One of the drivers is war, or "defense" as we say in modern times. The
second is the promise of economic return. And the third one is the praise of
either deity or royalty. I know of no exception to these three criteria. So
unless we are to believe that twenty-first century Americans are
fundamentally different from the humans that have ever lived in the history of
culture and civilization, then we should wise up to this fact that if we want to
go to the moon, Mars and beyond, and if that's going to be very expensive, it
ought to have one of those three drivers.
Now one of those drivers is no longer really possible in modern times. In
America we don't have kings, so it's not going to be in praise of royalty, and
praise of deity doesn't take on technological projects, except for architecture
where you get buildings like the cathedrals of Europe. So that leaves only two
possible drivers to turn a space program into a space enterprise. Either we do
it because we're in competition, or we do it because we see there is an
economic benefit from it. And rather than promote war by saying, "Let's hope
China builds military bases on Mars, so that we would then go to Mars," that
leaves private enterprise.
Left: Low earth orbit—the appeal of living in space? Image
credit: NASA. Right: Artist's conception of an early, preterraforming outpost for human visitors to Mars. Image
credit: Mark Dowman/JSC/NASA.
AM: More of that private enterprise you were talking about.
NT: That's right. As long as that kind of prize money continues to push an
envelope, there'll always be an interest in that frontier. And people say,
"We're not interested in the space program like we were in the 60s." Well,
duh! It's because we're not breaking any frontiers anymore.
AM: Do you notice there's more of an interest in pushing that frontier in the
private industry than among scientists themselves?
NT: By and large, scientists, and especially astrophysicists, are not especially
keen on sending people into space versus sending robots. You can't even have
that conversation.
AM: Really?
Private enterprise has already played a modest role in keeping a buoyant level
of space exploration afloat, with the launch vehicles and the satellite industry.
It's not a thriving industry, but it's there and it's real. Without the participation
of private enterprise, I think we can forget the whole thing and just go home.
Let the rest of the world pass us by technologically, and we'll sit at home
sucking our thumb and complaining that jobs are going overseas.
NT: Well, you can, but you're mixing apples and oranges. You're saying,
"How do you get the biggest space exploration bang for the buck?" Well, you
send a robot. We all agree about that. But then you say, "How do you get the
funding to do this in the first place?" You've got to send people. So you're
caught in this debate that's not really a debate. There's the reality of the
politics and there's the reality of the science. And the science is not getting
done at all without the politics. You have to honor the politics, otherwise
nobody's in business.
AM: So did you see the testimony of Ray Bradbury, where he said we must
explore to satisfy our craving for knowledge and adventure, to be overly
romantic?
AM: I guess people got scared about sending humans anywhere after the
recent Columbia disaster.
NT: It is, but you need some of that too. There are people who will join this
vision for romantic reasons without specific reference to economics or
politics. It's a richer vision when you can include the rest of these reasons.
I'm simply saying that the romantic reasons aren't enough to sustain funding
NT: The problem there is not that humans died, which itself is a tragedy. It's
that they died boldly going where hundreds had gone before. It's very
different to die being the first astronauts attempting to land and walk on Mars
than it is to be astronauts who died going into Low Earth Orbit. These are
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
very different ways to die. I don't believe the claim that we've lost our nerve.
If every next mission were pushing an envelope, you would have people lined
up around the block to take that risk.
5
Ebel and Grossman also drew upon the work of the University of Chicago's
Mark Ghiorso and the University of Washington's Richard Sack, who have
developed computer simulations that describe how minerals change under
high temperatures.
Read the original article at http://www.astrobio.net/news/article1497.html.
MYSTERY MINERALS FORMED IN FIREBALL FROM COLLIDING
ASTEROID THAT DESTROYED THE DINOSAURS
University of Chicago release
23 March 2005
Scientists at the American Museum of Natural History and the University of
Chicago have explained how a globe-encircling residue formed in the
aftermath of the asteroid impact that triggered the extinction of the dinosaurs.
The study, which will be published in the April issue of the journal Geology,
draws the most detailed picture yet of the complicated chemistry of the
fireball produced in the impact. The residue consists of sand-sized droplets of
hot liquid that condensed from the vapor cloud produced by an impacting
asteroid 65 million years ago. Scientists have proposed three different origins
for these droplets, which scientists call "spherules". Some researchers have
theorized that atmospheric friction melted the droplets off the asteroid as it
approached Earth's surface. Still others suggested that the droplets splashed
out of the Chicxulub impact crater off the coast of Mexico's Yucatan
Peninsula following the asteroid's collision with Earth.
But analyses conducted by Denton Ebel, Assistant Curator of Meteorites at the
American Museum of Natural History, and Lawrence Grossman, Professor in
Geophysical Sciences at the University of Chicago, provide new evidence for
the third proposal. According to their research, the droplets must have
condensed from the cooling vapor cloud that girdled the Earth following the
impact. Ebel and Grossman base their conclusions on a study of spinel, a
mineral rich in magnesium, iron and nickel contained within the droplets.
"Their paper is an important advance in understanding how these impact
spherules form," said Frank Kyte, adjunct associate professor of geochemistry
at the University of California, Los Angeles. "It shows that the spinels can
form within the impact plume, which some researchers argued was not
possible."
When the asteroid struck approximately 65 million years ago, it rapidly
released an enormous amount of energy, creating a fireball that rose far into
the stratosphere. "This giant impact not only crushes the rock and melts the
rock, but a lot of the rock vaporizes," Grossman said. "That vapor is very hot
and expands outward from the point of impact, cooling and expanding as it
goes. As it cools the vapor condenses as little droplets and rains out over the
whole Earth."
This rain of molten droplets then settled to the ground, where water and time
altered the glassy spherules into the clay layer that marks the boundary
between the Cretaceous and Tertiary (now officially called the Paleogene)
periods. This boundary marks the extinction of the dinosaurs and many other
species.
The work that led to Ebel and Grossman's Geology paper was triggered by a
talk the latter attended at a scientific meeting approximately 10 years ago. At
this talk, a scientist stated that spinels from the Cretaceous-Paleogene
boundary layer could not have condensed from the impact vapor cloud
because of their highly oxidized iron content. "I thought that was a strange
argument," Grossman said. "About half the atoms of just about any rock you
can find are oxygen," he said, providing an avenue for extensive oxidation.
Grossman's laboratory, where Ebel worked at the time, specializes in
analyzing meteorites that have accumulated minerals condensed from the gas
cloud that formed the sun 4.5 billion years ago. Together they decided to
apply their experience in performing computer simulations of the
condensation of minerals from the gas cloud that formed the solar system to
the problem of the Cretaceous-Paleogene spinels. UCLA's Kyte, who himself
favored a fireball origin for the spinels, has measured the chemical
composition of hundreds of spinel samples from around the world.
Ebel and Grossman built on on Kyte's work and on previous calculations done
by Jay Melosh at the University of Arizona and Elisabetta Pierazzo of the
Planetary Science Institute in Tucson, AZ, showing how the asteroid's angle
of impact would have affected the chemical composition of the fireball.
Vertical impacts contribute more of the asteroid and deeper rocks to the vapor,
while impacts at lower angles vaporize shallower rocks at the impact site.
After an asteroid measuring six miles in diameter collided with Earth 65
million years ago, the skies filled with a bizarre rain of calcium-rich,
silicate liquid droplets. This rain reflected the chemical content of the
vaporized rocks around the Chicxulub impact crater in Mexico. An
article published in the April 2005 issue of the journal Geology by
scientists at the American Museum of Natural History and the
University of Chicago describes how spinel minerals crystallized inside
the liquid spherules that condensed from the Chicxulub impact fireball.
The formation of the spinels has been scientifically controversial. This
series of images shows a spherule and mineral grains that condensed
from the fireball following the asteroid impact. The first two images are
photographs of a spherule that has been sliced and polished. The
dark areas are clay minerals and the bright, reflective grains are
spinels. The second image is a close-up of one side of the spherule.
The third image was taken by an electron microscope to show the
geometry of the spinel crystals. Image credits: Frank Kyte.
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
6
The resulting computer simulations developed by Ebel and Grossman show
how rock vaporized in the impact would condense as the fireball cooled from
temperatures that reached tens of thousands of degrees. The simulations paint
a picture of global skies filled with a bizarre rain of a calcium-rich, silicate
liquid, reflecting the chemical content of the rocks around the Chicxulub
impact crater. Their calculations told them what the composition of the
spinels should be, based on the composition of both the asteroid and the
bedrock at the impact site in Mexico. The results closely matched the
composition of spinels found at the Cretaceous-Paleogene boundary around
the world that UCLA's Kyte and his associates have measured.
Scientists had already known that the spinels found at the boundary layer in
the Atlantic Ocean distinctly differed in composition from those found in the
Pacific Ocean. "The spinels that are found at the Cretaceous-Paleogene
boundary in the Atlantic formed at a hotter, earlier stage than the ones in the
Pacific, which formed at a later, cooler stage in this big cloud of material that
circled the Earth," Ebel said.
The event would have dwarfed the enormous volcanic eruptions of Krakatoa
and Mount St. Helens, Ebel said. "These kinds of things are just very difficult
to imagine," he said.
The results in this paper strengthen the link between the unique Chicxulub
impact and the stratigraphic boundary marking the mass extinction 65 million
years ago that ended the Age of Dinosaurs. The topic will be explored further
in a new groundbreaking exhibition, "Dinosaurs: Ancient Fossils, New
Discoveries," set to open at the American Museum of Natural History on May
14. After it closes in the New York, the exhibition will travel to the Houston
Museum of Natural Science (March 3 - July 30, 2006); the California
Academy of Sciences, San Francisco (September 15, 2006 - February 4,
2007); The Field Museum, Chicago (March 30 - September 3, 2007); and the
North Carolina State Museum of Natural Sciences, Raleigh (October 26, 2007
- July 5, 2008).
Read the original news release at http://wwwnews.uchicago.edu/releases/05/050323.fireball.shtml.
Additional articles on this subject are available at:
http://www.space.com/scienceastronomy/050328_asteroid_impact.html
http://www.terradaily.com/news/deepimpact-04w.html
http://www.universetoday.com/am/publish/strange_minerals_impact.html
NEW FRONTIER OPENS IN THE SEARCH FOR LIFE ON OTHER
PLANETS
NASA/GSFC release
28 March 2005
Scientists recently discovered a new frontier in the race to find life outside our
solar system. Dying red giant stars may bring icy planets back from the dead.
Once-frozen planets and moons may provide a new breeding ground for life as
their stars enter the last, and brightest, phase of their lives. Previous ideas
about the search for extra-solar life had excluded these regions.
An international team of astronomers estimates that the emergence of new life
on a planet is possible within the red giant phase. "Our result indicates that
searches for life-giving worlds outside our solar system should include planets
around old stars," said Dr. Bruno Lopez of the Observatoire de la Cote d'Azur,
Nice, France. Lopez and his colleagues estimate that more than 150 red giant
stars are close enough—within 100 light years—for upcoming or proposed
missions to search for the signatures of life on distant worlds. A light year is
the distance light travels in one year, almost six trillion miles!
Location, location, location
One of the secrets of Earth's success in producing life is its location within the
sphere of the Sun's habitable zone. This sphere intersects the plane of the
solar system to create a special donut-shaped boundary that outlines where
water can exist as a liquid in our solar system, a necessity for the development
of life. Get too far from the Sun—and it's a lonely icebox. Too close—and
the water evaporates into space, never to return again.
While the Earth currently sits well within this donut of life, our Sun is
evolving and will one day grow to be a red giant star. Its habitable zone will
expand with it, changing the locales where liquid water can splash and life
may one day thrive.
Left: A sun-like star grows into its red giant phase, increasing in size
and luminosity. Energy in the form of heat can now reach a oncefrozen and dead moon. The icy surface quickly melts into liquid water,
filling in old craters with warmer seas. The stage is now set for the
possible formation of new life. Right: Our planet lies within the Sun's
habitable zone. This donut-shaped boundary outlines where water can
exist as a liquid in our solar system, a necessity for the development of
life. As the Sun develops into old age, its habitable zone will expand
with it, changing the locales where liquid water can splash and life may
one day thrive. Image credits: NASA.
In light of the Sun, Mars may be a sound investment
Lying just inside the outer limit of our Sun's habitable zone, Mars remains a
frozen world today because of its thin atmosphere. However, when the Sun
becomes a red giant a few billion years from now, Mars may become the
happening place to be. "Mars will be in the habitable zone for a couple billion
years, so martian life may get a second chance," said Dr. William Danchi of
NASA's Goddard Space Flight Center, Greenbelt, MD.
In 2003, researchers monitored the amount of ice on Mars during its winter
and spring seasons. In some regions, the water-ice content was more than
90% by volume. Scientists suspect that this water used to fill the planet's
now-dry lakes and seas. One day in the distant future, the frozen water on
Mars may fill these dry basins again and bring forth new life in our solar
system.
Red giants redefine the search for extra-terrestrial life
The same holds true for planets and moons as they orbit their own red giant
suns. Billions of years ago, these stars were similar to our Sun. Imagine the
events as they unfolded: A Sun-like star explodes into its red giant phase,
growing tremendously in size and brightness. Warm rays from the star reach
out to a once-frozen and dead moon. The solitary satellite's icy top layer
quickly melts into liquid water, which creeps across the surface and fills old
dusty craters with warmer seas. The stage is set for the birth of new life in the
moon's now-vibrant oceans.
Left: In 2003, researchers monitored the amount of water-ice on Mars,
which is more than 90% in some areas. Right: Researchers estimate
that the time required for the emergence of new life fits within the Red
Giant phase, adding to the number of stars that may have Earth-like
planets orbiting them. The Kepler Mission will look for tiny dips in the
brightness of a star when a planet crosses in front of it, known as a
transit. Image credits: NASA.
Currently, there are at least 150 red giant stars within 100 light years of Earth
and many of them may have orbiting planets capable of supporting life. A
new frontier has opened for planet-hunters around the world. One such
endeavor, NASA's Kepler mission, hopes to discover smaller Earth-like
planets outside our solar system. Looking for tiny dips in the brightness of a
star when a planet crosses in front of it, researchers will observe about
100,000 stars in one small patch of sky for four years. Kepler is set for launch
in 2007.
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
Read the original news release at
http://www.nasa.gov/centers/goddard/news/topstory/2005/0801frozenworlds.h
tml.
Additional articles on this subject are available at:
http://www.astrobio.net/news/article1503.html
http://www.spacedaily.com/news/extrasolar-05o.html
http://spaceflightnow.com/news/n0503/29planets/
http://www.universetoday.com/am/publish/dying_stars_second_chance.html
CENSORSHIP OF IMAX FILMS THREATENS INTEGRITY OF
SCIENCE, LEADER SAYS
From LiveScience
29 March 2005
The leader of the world's largest organization of scientists said the suppression
of some IMAX films because they run counter to religion threatens the
integrity of science and public education. Alan Leshner, CEO of the
American Association for the Advancement of Science and executive
publisher of the journal Science, sent a letter Monday to 410 members of the
Association of Science-Technology Centers. The letter prompted by recent
reports that IMAX theaters in at least a dozen U.S. cities have declined to
show films that endorse the science of evolution.
"We are writing now to express strong concerns about increasing threats to
science that endanger our shared missions and to offer our support and
partnership in dealing with them," Leshner's article said.
Read the full article at
http://www.livescience.com/othernews/050329_imax_letter.html.
CROSSING THE TREELINE
By Chris McKay
From Astrobiology Magazine
29 March 2005
Chris McKay, a planetary scientist at the Ames Research Center, has long
been investigating the coldest and driest places on Earth. These harsh
environments—and the ability of life to adapt there—could point the way to
finding life on Mars. McKay presented this lecture, entitled "Drilling in
Permafrost on Mars to Search for a Second Genesis of Life," at a NASA
Astrobiology Institute Director's Seminar on November 29, 2004. In this part
of his lecture, McKay describes one of the driest place on Earth and how one
tests for the equivalent of a bacterial "treeline" where microbes cannot thrive
in the Andes Mountains.
7
mountains in the middle, which block out the runoff from the Andes. This is a
very dry, virtually lifeless place.
In a normal desert, which gets about 25 millimeters of rain per year, there are
organics. You get bushes and even some ants. But the Mars Viking detector
of organics—the GCMS—would not be able to find life organics in the
Atacama. The level of organics is so low that we have to heat the sample to
find any. Viking heated samples to 500 degrees Celsius, but to find organics
at Atacama, we have to heat the sample to 750 degrees C.
The concentration of organics in the really dry part of Atacama is interesting,
because there seems to be a microbial "tree line". At the tree line on a
mountain, the trees suddenly stop, as though the mountain had been shaved.
In the driest part of the Atacama, the number of bacteria falls by four orders of
magnitude.
One of the Viking experiments added nutrients to the martian soil. There
were some soil reactions, and people today still argue about what happened.
Viking added both right and left-handed amino acids to the soil. Since life on
Earth is composed of left-handed, or L-chiral, amino acids, you can think of
the nutrients as good soup for life and bad soup. The idea was that if
something biological is there, you would expect it to eat the good, "lefthanded amino acid" soup. Life would show a higher uptake of good biology
soup. But in the Viking experiment, the two soups were mixed and we could
not tell if one was favored over the other.
We decided to duplicate this experiment on Earth, in the Atacama, adding a
similar soup of amino acids. Our experiment found no clear signs of life, but
had some interesting carbon reactions. At Atacama both kinds of soup are
consumed with equal gusto. This indicates a photo-chemically produced
oxidant, and not a biological reaction. Atacama is like Mars because the
addition of nutrients caused oxidized organics to increase. Also, virtually no
organisms are detectable, and no DNA.
At the Atacama, we don't drill, we dig. There is no detectable life on the
surface, but in pits, there is a layer where the bacterial count shoots up. We
don't know what is happening there. It could be a relic from the past. It could
be a water layer. It could be a habitable zone. This may be relevant to Mars.
The martian surface is cooked or bleached, but relic organic material may be
below the topsoil.
Read the original article at http://www.astrobio.net/news/article1502.html.
CLIMATE MODELS REVEAL INEVITABILITY OF GLOBAL
WARMING
By Sarah Graham
From Scientific American
29 March 2005
How to best curb greenhouse gas emissions is a hotly debated topic.
But new research suggests that putting the brakes on greenhouse gas
levels is not enough to slow down climate change because the ocean
responds so slowly to perturbations. The study results indicate that
even if greenhouse gas levels had stabilized five years ago, global
temperatures would still increase by about half a degree by the end
of the century and sea level would rise some 11 centimeters.
Read the full article at http://cl.exct.net/?ffcd16-fe5d15767c61067d761cfe28167073670175701c72.
ON AMMONIA AND ASTROBIOLOGY
By Jonathan Lunine
From Astrobiology Magazine
30 March 2005
Martian Frosty Dune Field MGS MOC Release
MOC2-713, 1 May 2004. Image Credit: Mars
Global Surveyor, Malin Space Systems.
I want to move from frozen ground to dry places. On the west coast of Chile
and Peru is the Atacama Desert, the driest place on Earth. It has a double rain
shadow. On the western side, the cold Pacific fog is blocked out, and on the
eastern side, rain is blocked out by the towering Andes. There are also
Jonathan Lunine, a professor of planetary science and physics at the
University of Arizona's Lunar and Planetary Laboratory in Tucson, Arizona,
is also an interdisciplinary scientist on the Cassini/Huygens mission. Lunine
presented a lecture entitled "Titan: A Personal View after Cassini's first six
months in Saturn orbit" at a NASA Director's Seminar on January 24, 2005.
This edited transcript of the Director's Seminar is Part 4 of a 4-part series.
The presence of features seen in Cassini's radar data would suggest that
ammonia is at work on Titan, powering cryovolcanism. Cryovolcanism—
water-ice volcanism—requires a liquid layer in the interior of Titan. It also
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
8
requires an agent to lower the melting point density and mobility of liquid
water. Ammonia does all these very well.
purines, pyrimidines and so on. That makes Titan an interesting object from
the point of view of astrobiology.
There are three things about liquid water that are bad as a volcanic fluid.
First, it only melts at 273 degrees Kelvin, which is a rather high temperature
for the interior of Titan to be reaching after accretion. Second, liquid water is
denser than water ice, so it's hard to get it out onto the surface. And third,
liquid water is very runny. It doesn't produce features like the one we see in
radar. But if you add ammonia to liquid water, at the right temperature you
get a material with the mobility, equivalent to that of basalt.
In the lab, tholins have been hydrolized and they do produce amino acids. But
how far has organic chemistry gone on the surface of Titan? If indeed
material is raining out from the stratosphere, then what happens to this
material at the surface? To what extent is any chemistry on the surface at all
relevant to the prebiotic chemistry that presumably occurred on the Earth prior
to the time life began?
Cassini was not really instrumented to answer these questions about Titan, but
they're excellent questions for a follow-up mission. The answers are
dependent on whether Cassini finds abundant organics on Titan's surface.
While the jury is still out on that, it's looking better and better from the
Huygens data and the orbiter data so far.
People have compared the reducing atmosphere of Titan with the classic
Miller-Urey experiment, which used water and ammonia with methane to
make all sorts of prebiotic molecules. But on Titan the water and ammonia
are frozen out, except when you have cryovolcanism.
Surface image from Titan shows ice blocks strewn around.
Image credit: ESA.
Ammonia not only reduces the mobility of the water, it also lowers the
melting point by 100 degrees Celsius. It's very easy to get a liquid ammonia
water layer in Titan's interior today; there's no problem with that energetically.
Furthermore, ammonia lowers the density of liquid water so that it's neutrally
buoyant relative to water ice.
One thing that Titan could not have done during its history is to have had a
liquid layer that then froze over. During the freezing process of this layer in
the interior, the tidal dissipation rate goes way up. This tidal dissipation
would have reduced the eccentricity of Titan's orbit, making it more
circularized than it is.
Titan may never have had a liquid layer in its interior, but that's hard to
countenance, even for a pure water ice object, because accretion would melt
the water, and then you get a re-freezing. The simplest explanation of why
Titan still has a non-zero eccentricity is that the liquid layer in its interior has
never frozen. The only way for it never to have been frozen is to have
ammonia that allows for that low melting point solution.
The Cassini orbiter ion neutral mass spectrometer and the Huygens gas
chromatograph mass spectrometer both sampled Titan's atmosphere, and
found there is essentially no non-radiogenic argon. There is argon-40 on
Titan, and it is a radiogenic decay product of potassium. It implies that there
has been outgassing from the interior of Titan. But there is no argon-36 or
argon-38 to the level of 10 parts per million.
Argon is abundant in the solar system—it's 10 percent the abundance of
nitrogen in solar composition. So you would expect that Titan's atmosphere
would have at least 1 percent if not 10 percent argon. Instead, it has four
orders of magnitude less than that. The most natural explanation is that the
nitrogen that helped form Titan was a much less volatile form, which was
easily attached to the ice, in a warm environment, which excluded argon. And
that candidate is ammonia.
So ammonia's the magic material. Now, if you have all these hydrocarbons
and nitriles on the surface of Titan, and occasional contact of these with liquid
water and liquid ammonia, by volcanism or impact, then chemistry possible
during that time might include the production of amino acids, sugars, HCN,
Stanley Miller's classic "primordial soup" experimental setup
with a simulated ocean, lightning and broth of hydrogen,
methane, ammonia and water.
The Miller-Urey experiment used electric sparks to simulate lightning
discharges. So far, there is no evidence for electrical discharges in Titan's
atmosphere. The atmospheric structure instrument on Huygens did have a
lightning detector. It detected one pulse, but it was right at the moment that
the main parachute pyros were fired, and that was probably the source of the
pulse. The energy available for weather on Titan is so small that the amount
of lightning that could be sustained at any given time is very small, though it
could be playing a role in the long term.
The next step beyond Cassini/Huygens, I think, is to go back to Titan with a
mobile platform that can sample some of this organic stuff on the surface, and
tell us whether any of it includes molecules of prebiotic interest.
Read the original article at http://www.astrobio.net/news/article1505.html.
CASSINI SIGNIFICANT EVENTS FOR 10-16 MARCH 2005
NASA/JPL release
18 March 2005
The most recent spacecraft telemetry was acquired today from the Goldstone
tracking station. The Cassini spacecraft is in an excellent state of health and is
operating normally. Information on the present position and speed of the
Cassini spacecraft may be found on the "Present Position" web page located at
http://saturn.jpl.nasa.gov/operations/present-position.cfm.
Science this week included a magnetospheric boundary campaign performed
by the Magnetospheric and Plasma Science (MAPS) instruments, and both
individual and joint observations performed by the Optical Remote Sensing
(ORS) instruments. Individual ORS observations included Far-IR Maps of
Saturn taken by the Composite InfraRed Spectrometer (CIRS), Visual and
Infrared Mapping Spectrometer (VIMS) observations of the E ring, Ultraviolet
Imaging Spectrograph (UVIS) mosaics of Saturn's inner magnetosphere, and
Imaging Science Subsystem (ISS) observations of Iapetus limb topography
and geodesy. VIMS, CIRS and ISS jointly performed radial scans of Saturn's
rings as Cassini crossed the ring plane on March 12, and ISS and UVIS
periodically performed joint observations of Dione, Enceladus, Mimas, Rhea
and Tethys.
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
Thursday, March 10:
Uplink Operations sent commands to the spacecraft today for an ISS Wide
Angle Camera memory readout and reload of Instrument Expanded Blocks,
power-off of the backup sun sensor assembly, and a Magnetospheric Imaging
Instrument (MIMI) Low Energy Magnetospheric Measurement Subsystem
(LEMMS) power cycle, sensor reset, and diagnostic mini-sequence.
The Spacecraft Operations Office performed a reaction wheel momentum
adjustment. Navigation delivered the final orbit determination solution for
Orbit Trim Maneuver (OTM) 17. The actual maneuver will take place
tomorrow evening.
Instrument Operations delivered ISS Flight Software Version 1.4 to the
Project Software Library. A delivery review will be held on April 15, with
uplink and in-flight test to occur in June. The Cassini Imaging Team's (ISS)
first scientific findings on Saturn's largest moon, Titan, are being published
today in the journal Nature.
9
Saturn's small, irregularly-shaped moon Epimetheus orbits against the
backdrop of the planet's rings, which are nearly edge-on in this view.
Some of the moon's larger geological features can be seen here.
Epimetheus is 116 kilometers (72 miles) across. The image was taken
in visible light with the Cassini spacecraft narrow-angle camera on
February 18, 2005, at a distance of approximately 990,000 kilometers
(615,000 miles) from Epimetheus and at a Sun-Epimetheusspacecraft, or phase, angle of 99 degrees. Resolution in the original
image was 6 kilometers (4 miles) per pixel. The image has been
contrast-enhanced and magnified by a factor of two to aid visibility.
Friday, March 11:
OTM-17 was completed on the spacecraft this evening. This maneuver, also
known as the "E1 + 3 days maneuver", is part of the E1-T7 10-maneuver
optimization chain. The main engine burn began at 8:31 PM PST. A "quick
look" immediately after the maneuver showed the burn duration was 2.822 sec
long, giving a delta-V of 0.42 m/s. ACS reported the burn termination was a
"nominal complete" with an accelerometer cutoff. Propulsion indicated the
burn was nominal. Tank pressures, temperatures, etc, were nominal. This
maneuver was performed in the "blow-down" mode, where the fuel and
oxidizer tanks were not directly connected to the helium pressurant source.
Thermal reported all nominal with temperatures recovering as expected.
Power margin throughout the maneuver was nominal. There was no
unexpected CDS or Fault Protection activity.
Monday, March 14:
Uplink Operations sent real-time commands to the spacecraft for a CDS
memory readout, to perform Cassini Plasma Spectrometer (CAPS) actuator
diagnostics, reset the MIMI LEMMS Sensor, and perform an INMS flight
software normalization procedure.
Tuesday, March 15:
Mission Assurance and Huygens Probe Operations presented a paper entitled
"Collaborative Risk Management for the Cassini-Huygens Probe Mission" at
last week's IEEE Aerospace Conference.
The paper described the
collaborative effort of risk management and risk mitigation employed by the
project. The talk was well received at the conference and it is hoped that the
approach implemented by the Cassini-Huygens team will serve as an example
for others who are implementing risk management during critical phases of
mission operations.
During its very close flyby of Enceladus on March 9, 2005, Cassini took
high resolution images of the icy moon that are helping scientists
interpret the complex topography of this intriguing little world. This
scene is an icy landscape that has been scored by tectonic forces.
Many of the craters in this terrain have been heavily modified, such as
the 10-kilometer-wide (6-mile-wide) crater near the upper right that has
prominent north-south fracturing along its northeastern slope. The
image has been rotated so that north on Enceladus is up. The image
was taken in visible light with the narrow angle camera from a distance
of about 11,900 kilometers (7,400 miles) from Enceladus and at a SunEnceladus-spacecraft, or phase, angle of 44 degrees. Pixel scale in
the image is 70 meters (230 feet) per pixel.
Cassini Outreach and Saturn Observation Campaign members participated in
Community Science Night at La Fetra Elementary School, a K-5 school with
720 students, in Glendora, CA. In addition to a school science fair, visitors
passed by a NASA image display, with 3-D glasses and lithographs for all.
They also enjoyed a petting zoo, and Saturn and moon observations under
perfect skies. The event also included the "Egg Stronauts Egg Drop" from
atop the tall ladder on a Los Angeles County Fire Truck, and featured the
kindergarten astronomy class's scale model of the solar system. Over 300
visitors to the telescopes received Saturn trading cards and Cassini
bookmarks.
Cassini Outreach also participated in a science fair at Barnhart School in
Arcadia, CA. Over 100 students in grades 1-6 submitted projects. The Los
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
Angeles Astronomical Society hosted viewing of Saturn and other celestial
bodies. All science fair participants received Cassini bookmarks.
This map of Titan's surface illustrates the regions that will be imaged
by Cassini during the spacecraft's close flyby of the haze-covered
moon on March 31, 2005. At closest approach, the spacecraft is
expected to pass approximately 2,400 kilometers (1,500 miles) above
the moon's surface. The colored lines delineate the regions that will be
imaged at different resolutions. Images from this encounter will include
the eastern portion of territory observed by Cassini's radar instrument
in October 2004 and February 2005. This will be the Cassini cameras'
best view to date of this area of Titan.
Wednesday March 16:
10
Soon after launch on January 12, 2005, Deep Impact entered the
commissioning phase. During that phase, the mission team verified the basic
state of health of all subsystems and tested the operation of science
instruments. The spacecraft's autonomous navigation system was activated
and tested using the moon and Jupiter as targets.
Four days after launch from Cape Canaveral on January 12, 2005, the
Deep Impact spacecraft pointed at the Moon to test its telescopes,
cameras and spectrometer. This image was taken on January 16,
2005, with the Medium Resolution Imager (MRI). It was a 9.5 sec
exposure. The spacecraft was more than 1.65 million kilometers (1.02
million miles) from the Moon, and a little more than 1.27 million
kilometers (789,000 miles) from Earth. The spacecraft is scheduled to
impact comet Tempel 1 on July 4, 2005. Image credit: NASA/JPL.
An S12 Science Operations Plan Update wavier disposition meeting was held
on Wednesday. Project Management approved the two waivers under
consideration. In support of S10, SCO performed an Integrated Test Lab
(ITL) test of the Titan-5 closest approach sequence for the April 16, 2005
encounter.
The ITL has also been busy performing ACS Flight Software A8.7.2 updates
planned for a late May 2005 uplink. This version will update maneuver
telemetry scale factors to improve visibility during smaller main engine
maneuvers. A8.7.2 will also update the guidance and control detumble
vectors for more accurate control late in the mission.
Check out the Cassini web site at http://saturn.jpl.nasa.gov for the latest press
releases and images. Further updates to the education section and the K-4
program
pages
were
posted
live
this
week
at
http://saturn.jpl.nasa.gov/education/index.cfm.
The Cassini-Huygens mission is a cooperative project of NASA, the European
Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory,
a division of the California Institute of Technology in Pasadena, manages the
Cassini-Huygens mission for NASA's Science Mission Directorate,
Washington, DC. JPL designed, developed and assembled the Cassini orbiter.
Additional articles on this subject are available at:
http://www.spacedaily.com/news/cassini-05zh.html
http://spaceflightnow.com/cassini/050321serenity.html
http://spaceflightnow.com/cassini/050321hyperion.html
http://spaceflightnow.com/cassini/050323dione.html
http://spaceflightnow.com/cassini/050324enceladus.html
http://spaceflightnow.com/cassini/050326janus.html
http://www.universetoday.com/am/publish/cassini_mimas_eclipse.html
DEEP IMPACT MISSION STATUS REPORT
NASA release 05-086
25 March 2005
NASA's Deep Impact spacecraft completed the commissioning phase of the
mission and has moved into the cruise phase. Deep Impact mission planners
have separated the spacecraft's flight operations into five mission phases.
Cruise phase will continue until about 60 days before the encounter with
comet Tempel 1 on July 4, 2005.
An old favorite, Jupiter, was observed by Deep Impact on February 6,
2005, with its high resolution imager (HRI). Jupiter was over
728,000,000 million kilometers (more than 452,000,000 million miles)
away from the spacecraft. The North Polar Region, North Equatorial
Belt, South Equatorial Belt and South Polar Region can be seen as
dark regions and bands. The light regions are the tropical and
equatorial zones. Image credit: NASA/JPL.
The spacecraft's high gain antenna, which will relay images and data of the
cometary collision, was activated and is operating properly. A trajectory
correction maneuver was performed, refining the spacecraft's flight path to
comet Tempel 1. The maneuver was so successful that a second one planned
for March 31 was cancelled.
Another event during commissioning phase was the bake-out heating of the
spacecraft's High Resolution Instrument (HRI) to remove normal residual
moisture from its barrel. The moisture was a result of absorption into the
structure of the instrument during the vehicle's last hours on the launch pad
and its transit through the atmosphere to space.
At completion of the bake-out procedure, test images were taken through the
HRI. These images indicate the telescope has not reached perfect focus. A
special team has been formed to investigate the performance and to evaluate
activities to bring the telescope the rest of the way to focus. Future calibration
tests will provide additional information about the instruments' performance.
The Deep Impact spacecraft has four data collectors to observe the effects of
the collision: a camera and infrared spectrometer comprise the High
Resolution Instrument; a Medium Resolution Instrument (MRI); and a
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
duplicate camera on the Impactor Targeting Sensor (ITS). They will record
the vehicle's final moments before it is run over by comet Tempel 1 at
approximately 23,000 mph. The MRI and ITS are performing as expected.
11
answer basic questions about the formation of the solar system. The effects of
the collision will offer a better look at the nature and composition of these
celestial travelers.
The University of Maryland provides overall mission management for this
Discovery class program. Project management is handled by JPL. The
spacecraft was built for NASA by Ball Aerospace & Technologies
Corporation, Boulder, CO.
For more information about Deep Impact on the Internet, visit
http://www.nasa.gov/deepimpact. For more information about NASA on the
Internet, visit http://www.nasa.gov.
Contacts:
Dolores Beasley
NASA Headquarters, Washington, DC
Phone: 202-358-1753
D. C. Agle
Jet Propulsion Laboratory, Pasadena, CA
Phone: 818-393-9011
Artist Pat Rawlings gives us a look at the moment of impact and the
forming of the crater. Image credit: P. Rawlings/NASA.
"This in no way will affect our ability to impact the comet on July 4," said
Rick Grammier, Deep Impact project manager at NASA's Jet Propulsion
Laboratory (JPL), Pasadena, Calif. "Everyone on the science and engineering
teams is getting very excited and looking forward to the encounter."
Dr. Michael A'Hearn of the University of Maryland, College Park, MD,
added, "We are very early in the process of examining the data from all the
instruments. It appears our infrared spectrometer is performing spectacularly,
and even if the spatial resolution of the High Resolution Instrument remains at
present levels, we still expect to obtain the best, most detailed pictures of a
comet ever taken."
Looking down upon the Solar System from above (plane view), this
image shows the orbital path of Earth, Mars, Comet Tempel 1 and
Jupiter. The positions of the Earth at launch and encounter are
marked with a solid circle as is the comet at encounter. Image credit:
Tony Farnham.
Deep Impact is comprised of two parts, a flyby spacecraft and a smaller
impactor. The impactor will be released into the comet's path for the planned
high-speed collision. The crater produced by the impactor is expected to
range from the width of a house up to the size of a football stadium and be
from two to 14 stories deep. Ice and dust debris will be ejected from the
crater revealing the material beneath. Along with the imagers aboard the
spacecraft, NASA's Hubble, Spitzer and Chandra space telescopes, along with
the largest telescopes on Earth, will observe the effects of the material flying
from the comet's newly formed crater.
An intimate glimpse beneath the surface of a comet, where material and debris
from the formation of the solar system remain relatively unchanged, will
Additional articles on this subject are available at:
http://www.astrobio.net/news/article1500.html
http://www.space.com/missionlaunches/050325_deep_impact.html
http://www.spacedaily.com/news/comet-05h.html
http://spaceflightnow.com/news/n0503/25deepimpact/
MARS EXPRESS: THE MEDUSA FOSSAE FORMATION ON MARS
ESA release
29 March 2005
These images, taken by the High Resolution Stereo Camera (HRSC) on board
ESA's Mars Express spacecraft, show part of the Medusa Fossae formation
and adjacent areas at the highland-lowland boundary on Mars. The HRSC
obtained these images during orbit 917 with a resolution of approximately 13
meters per pixel. The scenes show an area located at about 5º South and 213º
East.
Medusa Fossae formation as seen by Mars Express.
The Medusa Fossae formation is an extensive unit of enigmatic origin found
near the martian "highland-lowland dichotomy boundary" between the Tharsis
and Elysium centers of volcanic activity. This dichotomy boundary is a
narrow region separating the cratered highlands, located mostly in the
southern hemisphere of Mars, from the northern hemisphere's lowland plains.
The cratered highlands stand two to five kilometers higher than the lowland
plains, so the boundary is a relatively steep slope. The processes that created
and modified the dichotomy boundary remain among the major unanswered
issues in Mars science.
The boundary between the old volcanic plateau region and part of the
widespread deposits of the Medusa Fossae formation, called Amazonis Sulci,
is shown in this image. In general, the formation appears as a smooth and
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
gently undulating surface, but is partially wind-sculpted into ridges and
grooves, as shown in the mosaic of nadir images.
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A bolide is any extraterrestrial body in the 1-10 kilometer size range, which
impacts on a planetary surface, explodes on impact and creates a large crater.
This is a generic term, used when we do not know the precise nature of the
impacting body, whether it is a rocky or metallic asteroid, or an icy comet, for
example.
The color images have been derived from the three HRSC color channels and
nadir channel. The perspective views have been calculated from the digital
terrain model derived from the stereo channels. The anaglyph image was
calculated from the nadir and one stereo channel. Image resolution has been
decreased for use on the internet.
Read the original news release at
http://www.esa.int/SPECIALS/Mars_Express/SEMSSZRMD6E_0.html.
Additional articles on this subject are available at:
http://www.universetoday.com/am/publish/medusa_fossae_mars.html
MARS GLOBAL SURVEYOR IMAGES
NASA/JPL/MSSS release
17-23 March 2005
Medusa Fossae—perspective view looking southwest.
The following new images taken by the Mars Orbiter Camera (MOC) on the
Mars Global Surveyor spacecraft are now available.
South Polar Cap (Released 17 March 2005)
http://www.msss.com/mars_images/moc/2005/03/17/
Frost on Dunes (Released 18 March 2005)
http://www.msss.com/mars_images/moc/2005/03/18/
5K Crater (Released 19 March 2005)
http://www.msss.com/mars_images/moc/2005/03/19/
Layers of Candor (Released 20 March 2005)
http://www.msss.com/mars_images/moc/2005/03/20/
Dunes of the Frozen North (Released 21 March 2005)
http://www.msss.com/mars_images/moc/2005/03/21/
Mars at Ls 176 Degrees (Released 22 March 2005)
http://www.msss.com/mars_images/moc/2005/03/22/
Left: This image, taken by the High Resolution Stereo Camera (HRSC)
on board ESA’s Mars Express spacecraft, shows a detail of the
Medusa Fossae formation. Here the volcanic plateau fed by the
southernmost Tharsis Montes volcano Arsia Mons, is dissected by
several valleys which were most likely carved by running water. Here
the Senus Vallis is shown in detail as an example where the lateststage inner channel is still visible. Right: This image, taken by the
High Resolution Stereo Camera (HRSC) on board ESA’s Mars
Express spacecraft, shows a detail of the Medusa Fossae formation.
This is the mouth of Abus Vallis, a channel of the same type as in the
left image. Here the walls are too steep or the valley too narrow to
look down to the bottom of the channel due to insolation and shading
of the image, but the remains of the last stage of water activity can be
traced as a small channel at the floor of the lowland plain. Additionally
the emplacement of pyroclastic flows is visible in this detail. It shows
that the action of water erosion ended before the emplacement of the
pyroclastic flow. The HRSC obtained these images during orbit 917
with a resolution of approximately 13 meters per pixel. It shows an
area located at about 5º South and 213º East. Image credits:
ESA/DLR/FU Berlin (G. Neukum).
It is commonly agreed that the materials forming Medusa Fossae were
deposited by pyroclastic flows or similar volcanic ash falls. The plateau walls
of the volcanic massif are partly covered by lava flows and crossed in places
by valleys which were most likely carved by fluvial activity. The remains of
water-bearing inner channels are visible in the centre of the valleys and at the
bottom of the massif. Superposition of the lobe-fronted pyroclastic flows
indicates that the water erosion ended before their deposition. Later, a
"bolide" impacted near the massif and the ejecta blanket was spread as a flow
over parts of the plateau, implying water or ice was present in the subsurface
at the time of impact.
Tharsis Channels (Released 23 March 2005)
http://www.msss.com/mars_images/moc/2005/03/23/
All of the Mars Global Surveyor images
http://www.msss.com/mars_images/moc/index.html.
are
archived
at
Mars Global Surveyor was launched in November 1996 and has been in Mars
orbit since September 1997. It began its primary mapping mission on March
8, 1999. Mars Global Surveyor is the first mission in a long-term program of
Mars exploration known as the Mars Surveyor Program that is managed by
JPL for NASA's Office of Space Science, Washington, DC. Malin Space
Science Systems (MSSS) and the California Institute of Technology built the
MOC using spare hardware from the Mars Observer mission. MSSS operates
the camera from its facilities in San Diego, CA. The Jet Propulsion
Laboratory's Mars Surveyor Operations Project operates the Mars Global
Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics,
from facilities in Pasadena, CA and Denver, CO.
MARS ODYSSEY THEMIS IMAGES
NASA/JPL/ASU release
21-25 March 2005
Cerberus Fossae (Released 21 March 2005)
http://themis.la.asu.edu/zoom-20050321a.html
Fractures in Tharsis Tholus (Released 22 March 2005)
http://themis.la.asu.edu/zoom-20050322a.html
Arcuate Fractures in Olympus Mons Caldera (Released 23 March 2005)
http://themis.la.asu.edu/zoom-20050323a.html
Marsbugs: The Electronic Astrobiology Newsletter, Volume 12, Number 11, 30 March 2005
Arcuate Fractures (Released 24 March 2005)
http://themis.la.asu.edu/zoom-20050324a.html
Ridges From Fractures (Released 25 March 2005)
http://themis.la.asu.edu/zoom-20050325a.html
All of the THEMIS images are archived at http://themis.la.asu.edu/latest.html.
NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission
for NASA's Office of Space Science, Washington, DC. The Thermal
Emission Imaging System (THEMIS) was developed by Arizona State
University, Tempe, in collaboration with Raytheon Santa Barbara Remote
Sensing. The THEMIS investigation is led by Dr. Philip Christensen at
Arizona State University. Lockheed Martin Astronautics, Denver, is the
prime contractor for the Odyssey project, and developed and built the orbiter.
Mission operations are conducted jointly from Lockheed Martin and from
JPL, a division of the California Institute of Technology in Pasadena.
End Marsbugs, Volume 12, Number 11.
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