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Transcript
Waiting for their spaceships to come in…
Dawn
Ceres
2015
New
Horizons
Pluto
2015
Vesta
2011
…with help from Hubble in the meanwhile
Citation from IAU Minor Planet Circular 56612 on the naming of
Asteroid “6815 Mutchler”
Asteroids
“ready for their close-up”
Max Mutchler
Head, Research & Instrument Analysis Branch
Space Telescope Science Institute
Public Lecture, 1 March 2011
Asteroids
“ready for their close-up”
Max Mutchler
Head, Research & Instrument Analysis Branch
Space Telescope Science Institute
Public Lecture, 1 March 2011
“I’m ready for my close-up, Mr. DeVille”
"I am big, it's the pictures that got small!"
- Gloria Swanson
“I’m ready for my close-up, Dawn”
"I am small, it's the pictures that got big!"
- Asteroid Vesta
Asteroid history and mystery
• Ceres, Vesta, Pallas,
discovered in early 1800s
• Called planets for 50
years, then re-classified:
any déjà vu ?
• Key to understanding
Solar System formation
…and us
• Giveth: our oceans?
• Taketh away: Killed the
dinosaurs? Still a threat?
• Exploration with Hubble,
Dawn…and astronauts?
The largest Kuiper Belt Objects,
and asteroids (or “protoplanets”)
Ceres
Vesta
Are they planets?
Ceres and Pluto: The “ugly duckling”
problem of being the first of an entire class
Asteroid Belt
Kuiper Belt
Discovered 1801-1851
Discovered in 1992
Ceres
Asteroids:
Main Asteroid Belt
typically rocky, with
circular orbits
between Mars
and Jupiter…
…but there are some
icy “Main Belt Comets”,
and Near-Earth Objects
Hubble images of Ceres reveal
roundness, surface features, and colors
Hubble WFPC2 images of asteroid Vesta in May 2007: color composite movie
Hubble WFC3 images of asteroid Vesta in 2010: color composite movie
Dawn will spend several months in
polar orbit around Vesta, before leaving
for Ceres.
Over the last 16 years, Hubble
observations have helped refine
Vesta’s pole position, which can give
Dawn extra time to do science, rather
than making orbit adjustments.
A more accurate knowledge of the pole
position will also help identify when the
extreme latitudes will have the best
possible solar illumination, and are
“ready for their close-up” .
Improved Measurement of asteroid 4 Vesta’s rotational axis orientation
Jian-Yang Li,, Peter C. Thomas, Brian Carcich, Max J. Mutchler,
Lucy A. McFadden, Christopher T. Russell, Stacy S. Weinstein-Weiss,
Marc D. Rayman, Carol A. Raymond , 2010, Icarus
Dawn mission overview
•
•
•
•
•
•
•
“Star Wars” ion
propulsion allows for
asteroid-hopping
Launch 27 Sep 2007
Mars boost 2009
Orbit Vesta 2011-12
Orbit Ceres 2015
Pallas: can’t get there
from here (anymore)
Note: New Horizons
Pluto flyby July 2015
So…why care about rocks in space?
We shall not cease from exploration
and the end of all our exploring
will be to arrive where we started
and know the place for the first time.
-- T. S. Eliot
We see evidence of ongoing star formation in our
own galaxy and other galaxies
These jets indicate a star forming inside this cloud
Our Sun forming from the collapse of a cloud of gas
and dust, forms a rotating disk
Asteroids and comets are
some of the best-preserved
“fossils” from the early Solar System
Further collapse within the disk form the icy gas
giant planets further out, beyond the “snow line”
The rocky terrestrial planets form closer in
There is evidence on Earth that planet formation
involved violent collisions and impacts
Since the moon has no weather (erosion), the
impact history is preserved much better
So we can surmise that the early Earth had no
oceans, and was not hospitable to life
After the heaviest bombardment was over, later asteroid and
comet impacts may have delivered water and organic material
to Earth – the stuff of life
Water Ice Discovered on Asteroid for First Time
By Clara Moskowitz
SPACE.com Senior Writer
28 April 2010
Water ice has been found on the surface of a nearby asteroid for the first
time – a discovery that could help explain how Earth got its oceans.
Two teams of researchers independently verified that the asteroid 24
Themis – a large rock hurtling through space in the asteroid belt between
Mars and Jupiter – is coated in a layer of frost. They also found that the
asteroid contains organic material, including some molecules that might
be ingredients for life.
The discovery might even provide clues about the origin of water on
Earth. "Our data are certainly at least consistent with the idea that you
could bring in plenty of water from impacts,“ said Andrew Rivkin of Johns
Hopkins University.
Asteroid Scheila:
a “Main Belt Comet”
In the wee hours of December 11th, University
of Arizona astronomer Steve Larson was on
cosmic patrol with the Catalina Sky Survey's
Schmidt telescope. That's when he noticed
something odd about the appearance of the
main-belt asteroid 596 Scheila. The asteroid
was clearly fuzzy, with a soft glow extending a
few arcminutes to the west and north. Other
astronomers quickly confirmed the cometary
appearance. If Scheila is truly a long-dormant
comet, then it's a big one: current estimates put
its diameter at 70 miles (113 km).
"It's a main-belt comet, although I don't know
what type yet," Dave Jewitt explains. He says it
could have resulted from an impact (as
occurred earlier this year with P/2010 A2) or
outgassing (as occurs on 133P/Elst-Pizarro).
The Whole Shebang
The Earth (and life on it) has always been directly influenced
by events in the larger universe…and always will be
Uh oh! You might want to pay more attention
to those space rocks than we did !!!
The dinosaurs got a warning shot….
…before they met their fate
Research by Dr. William F. Bottke, Dr. David Vokrouhlicky and
Dr. David Nesvorny suggests that the impactor believed to have
wiped out the dinosaurs and other life forms on Earth 65 million
years ago can been traced back to a breakup event in the main
asteroid belt.
A main-belt comet?
No, an asteroid collision…
“A recent disruption of the main-belt asteroid P/2010 A2”
David Jewitt, Harold Weaver, Jessica Agarwal,Max Mutchler & Michal Drahus,
Nature, Volume 467, 14 October 2010
Illustration by
Anne Feild, STScI
Big collisions in the
early Solar System
• Earth-Moon formation
• Pluto and moons
• Vesta impact: created
50 smaller asteroids,
20% of meteorites…
and any moons?
Hubble reveals two new Pluto moons in 2005
Charon, Nix, and Hydra likely formed by
collision…so Vesta should have moons too?
dwarf planet
asteroid
(small solar system body)
Hey, no fair!
But they are both “proto-planets”
Same initial conditions, but different subsequent evolutions
Vesta’s impact crater,
volcanic maria, dry?
Thomas, P. et al., 2005, “Differentiation of the asteroid Ceres as revealed by its shape”, Nature Letters, Vol 437
Thomas, P. et al., 1997, “Impact excavation on asteroid 4 Vesta: Hubble Space Telescope results”, Science, Vol 277
So Vesta should
have moons, right?
Satellite search
with Hubble’s
WFPC2 camera,
and with Dawn
as it approaches
in July
Hill sphere
(orbital stability zone)
Rosetta flyby of
asteroid 21 Lutetia
on 7 July 2010
Hubble moon search for
asteroid 21 Lutetia: a cautionary tale
An optical “ghost”…
not a moon!
Ongoing impacts and near-misses
Comet Shoemaker-Levy 9 impacts Jupiter in July 1994,
shortly after the 1st Hubble servicing mission
What if Comet SL9 hit
Earth instead of
Jupiter?
Much less likely, but
maybe we should try to
understand these events?
Our fears
(fueled by sci-fi)
This week’s New Yorker magazine
Fireball over Wisconsin on 14 April 2010:
caused by an object only ~1 meter in diameter
About 100 tons per day impacts the Earth, in small pieces
The animation consists of 34 radar images of near-Earth asteroid 2010 JL33 taken
by the Goldstone radio telescope on December 11 and 12, 2011. According to the
JPL website, the radar observations reveal that "2010 JL33 is an irregular,
elongated object roughly 1.8 kilometers wide that rotates once every nine hours."
To alter the orbit of a
killer asteroid, we’d
need to discover it
decades before
impact, not days
This kinda stuff takes
serious time and money…
…gee, almost as much as
a Hollywood movie budget!
Apophis
The 2029
“doomsday”
asteroid you may
have heard of
Near Earth Objects
(NEOs) are ideal for
study and exploration
…as long as they
don’t get too near!
Discovering NEOs….from space?
NASA's New Asteroid Mission Could Save the Planet
By Tariq Malik SPACE.com Managing Editor
16 April 2010
President Barack Obama set a lofty next goal this week for Americans in space: Visiting an asteroid by
2025. But reaching a space rock in a mere 15 years is a daunting mission, and one that might also carry the
ultimate safety of the planet on its shoulders. "By 2025, we expect new spacecraft designed for long journeys
to allow us to begin the first-ever crewed missions beyond the moon into deep space," Obama said. "We'll
start we'll start by sending astronauts to an asteroid for the first time in history.“
Astrophysicist John Grunsfeld – a former NASA astronaut who three shuttle missions to fix the Hubble
Space Telescope – suggested sending humans to purposely move an asteroid, to nudge the space rock to
change its trajectory. Such a feat, he said, would show that humanity could deflect a space rock if one
threatened to crash into the planet.
Scientists estimate there are about 100,000 asteroids and comets near Earth, but only about 20,000 are
expected to pose any risk of impact. NASA has found about 7,000 of those objects, 1,000 of them flying in
orbits that could potentially threaten the Earth in the future, NASA scientists have said. Astronomer Donald
Yeomans, head of NASA's Near-Earth Object program office at NASA's Jet Propulsion Laboratory in
Pasadena, Calif., said there are about a dozen near-Earth asteroids that could be within reach of manned
spacecraft, but most of those are relatively small. To make a crewed mission worth it, the target space rock
would likely have to be at least 300 feet (100 meters) wide. For comparison, the space rock that exploded in
a magnificent fireball over Wisconsin this week was just 3 feet (1 meter) wide, Yeomans said.
But there are secrets locked away on asteroids that may hold the key to understanding the formation of the
solar system. Asteroids are the thought to be the leftover remnants of the solar system's buildings blocks.
The organic molecules and compounds on them may offer clues on how life began on Earth, and if it's
possible elsewhere in the universe.
August 2, 2010
Apply Flexible Path to Near-Earth Objects
Daniel R. Adamo
•
•
•
•
•
•
Mandates to catalog NEOs in 1998 and 2005
IR space telescope in Venus-like orbit to discover most NEOs
2010 Presidential endorsement for a mission in 2025 – but don’t pick a date!
Asteroid within 0.1 AU > 50 m (only 3% of known), duration < 180 days,
minimize delta-V (velocity changes)
Asteroid 1999 AO10 example…try Space Game (citizen science)
Precursor “scout” missions to characterize object, and manage
potential hazards for astronauts:
• Mass, gravity field, spin: complicated orbit and approach?
• Moons or debris ring: spacecraft hazard?
• Volatiles beneath the surface (dormant comet)? No jets please!
Deep Impact / EPOXI
flyby of Comet Hartley
on Nov 4
Closest near-Earth
comet in decades!
Robotic precursor
missions needed to
identify suitable NEOs
for humans to visit
Hayabusa visits
asteroid Itokawa
Asteroids and comets
visited by spacecraft
Space Station compared to Comet Hartley 2
We don’t want to send astronauts
to asteroids that might be dormant comets!
What might a
human mission to a
near-Earth asteroid
look like?
Illustration: IHMC
An “easy” 2025 destination:
Near-Earth asteroid
1999 AO10
“co-orbiting” with Earth
Profile of a 6-month mission
to a near-Earth asteroid