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News • Mission Update
Space Shorts
Milky Way bubbly
Citizen scientists have found
more than 5000 “bubbles”
blown in gas and dust by young
hot stars. This is 10 times more
than previous surveys had
suspected, suggesting that we
live in a much more active starforming galaxy than had been
thought. The Milky Way Project
uses volunteers to look through
Spitzer Space Telescope data
and spot the wispy arcs, broken
rings and circle-within-circle
structures characteristic of
star-forming regions. People
are much better at this than
computers, and the project
also uses “crowd-sourcing”,
requiring at least five volunteers
to identify a structure as a bubble
before adding it to the database.
The volume of data from this
project is allowing researchers
to identify hierarchies in bubble
formation, for example, and hints
at structural complexities within
the Milky Way.
Mission update
http://www.milkywayproject.org
GRAIL gets going
NASA’s twin lunar orbiters
GRAIL (Gravity Recovery And
Interior Laboratory) began their
science data collection mission
in March. GRAIL will give a much
clearer picture of the internal
structure and composition of the
Moon from measurements of
the lunar gravitational field. The
two satellites, called Ebb and
Flow, will map the whole gravity
field three times, changing their
orbits and orbital separations
until 29 May, when the science
mission finishes.
http://www.nasa.gov/grail
BGS joins ESA Swarm
The British Geological Survey
has been successful in its bid
to join the European Space
Agency’s Swarm magnetic
survey mission validation team
as a principal investigator. BGS
will now be working with the
geophysical surveys carried out
with Swarm, a three-satellite
“mini constellation” that will
provide unprecedented spatial
and temporal resolution of the
Earth’s magnetic field. The data
will refine geomagnetic field
models and boost knowledge
of Earth’s interior and climate.
Swarm is currently set for
launch on 17 July 2012, and the
mission is expected to last up to
five years.
http://bit.ly/2VsaN
2.8
Clouds around Titan’s north pole clearing as spring arrives. (NASA/JPL-Caltech/Univ. Arizona/CNRS/LPGNantes)
Cassini at Titan:
collected works
Five years of data collected by the
NASA spacecraft Cassini have
shown how clouds, presumed to
be of ethane, around Titan’s north
pole have gradually dispersed as
winter turned to spring. Stephane
Le Mouelic, a Cassini team associate at the French National Center for
Scientific Research (CNRS) at the
University of Nantes, showed how
the clearing clouds have revealed
far more of the “Lake District” in
Titan’s northern hemisphere, notably
the large body of liquid hydrocarbon
known as Kraken Mare.
Valeria Cottini, a Cassini associate based at Goddard, used data
from Cassini’s composite infrared
mapping spectrometer to measure a
day-to-night temperature variation
of 1.5 K. Although this is not a large
variation around the typical 94 K
at the surface, it shows that diurnal
changes are part of the daily rhythm
of the weather on Titan, albeit on
days that last 16 times the length of
a day on Earth.
Another instrument on Cassini, the
radio science experiment, provided
data that helped Dominic Fortes at
University College London to model
the interior of the moon. Fortes
found evidence for differentiation
within Titan, giving it a dense core
that is probably rocky or a rock–ice
mixture. Magnetometer data from
Cassini also suggest a relatively cool,
wet, rocky interior. Together the data
suggest that an iron core is unlikely.
However, the new models suggest
problems with the origin of methane
in the atmosphere, as they suggest it
would remain in the core.
The research is published in a special issue of Planetary and Space Science: Titan through Time.
http://tinyurl.com/titanmoods
Cassini analyses
oxygen at Dione
Further evidence of oxygen in Saturn’s system of rings and moons has
come from NASA’s Cassini spacecraft, which has found a very tenuous atmosphere around the moon
Dione – with molecular oxygen
ions at a density of around 1 ion per
11 cubic centimetre of space.
Oxygen has become a feature of
Saturn and its moons, with both
the rings and the moon Rhea identified as sources of molecular oxygen.
Dione’s neutral atmosphere is about
as dense as Earth’s atmosphere at an
altitude of 480 km. Hubble Space
Telescope observations had detected
ozone around Dione, so the moon
was expected to be a source of oxygen, but it took Cassini’s plasma
spectrometer to detect the ions
directly on a flyby 500 km above the
surface of the moon.
The oxygen appears to come from
either solar photons or cosmic rays
bombarding the water ice that makes
the moon’s surface and liberating
oxygen molecules, although other
geological processes may be responsible. Either way, it is clear that oxygen itself is not necessarily a sign of
life elsewhere in the solar system.
http://www.nasa.gov/cassini
http://saturn.jpl.nasa.gov
Spitzer spots
solid buckyballs
Buckminsterfullerene – a 3D carbon
molecule shaped like a football and
containing up to 60 atoms – has been
found in space in solid form, with the
individual hollow buckyballs stacked
together like oranges in a crate.
The data come from the Spitzer
Space Telescope, which in 2010
A&G • April 2012 • Vol. 53
News • Mission Update
Twinkle twinkle little protostar
A combination of data from
NASA’s Spitzer Space Telescope and
ESA’s Herschel Space Observatory
has produced this more complete
image of star formation in the
Orion Nebula. Spitzer data cover
shorter infrared wavelengths than
Herschel, but combining the two,
as in this false-colour image, can
show the temperatures of dust in a
region of star formation. Warmer
A&G • April 2012 • Vol. 53 objects picked out by Spitzer
(at 8 and 24 mm) are shown in
blue, while progressively colder
regions from Herschel data show
in green and then red (70 and
160 mm respectively). Repeated
observations with Herschel (weekly
for six weeks in the spring of 2011)
showed that the brightness of the
young stars varied by as much as
20%. This is puzzling because it
represents fast changes in relatively
cool dust, probably in the outer disc
or gas envelope far from the hot
young star itself.
How does material that is
relatively cool and far from the
star heat up so quickly? Models of
star formation suggest timescales
of hundreds of years, rather than a
matter of weeks. One possibility is
that lumpy filaments of gas funnel
from the outer to the central regions
of the star, temporarily warming
the object as the clumps hit its
inner disc. Or perhaps material
occasionally piles up at the inner
edge of the disc and casts a shadow
on the outer disc. (NASA/ESA/JPLCaltech/IRAM)
http://www.herschel.caltech.edu
http://www.nasa.gov/herschel
http://www.esa.int/SPECIALS/Herschel
2.9
News • Mission Update
Space Shorts
Kepler wins prizes
NASA’s Kepler mission has been
awarded prizes by the Space
Foundation and Aviation Week.
The Space Foundation awarded
the planet-finding mission its
2012 John L “Jack” Swigert, Jr
Award for Space Exploration, in
recognition of the discovery of
61 comfirmed planets and more
than 2300 planet candidates, in
its first 16 months of operations.
Jack Swigert was one of the
astronauts on Apollo 13 and was
later elected to the US House
of Representatives. Kepler
was also named winner of the
2012 Aviation Week Laureate
Award, in the Space category.
The Laureate Awards recognize
individuals and teams for
extraordinary accomplishments
that embody the spirit of
exploration, innovation and
vision.
http://www.nasa.gov/kepler
Magnetosphere works
It’s a given that Earth’s
magnetosphere protects the
atmosphere from the erosive
effects of the solar wind. But
how big is the effect? A chance
alignment of Earth and Mars
in the same burst of energetic
plasma from the Sun in 2008
allowed ESA scientists to use
Mars Express and Cluster data to
find out. The solar wind pressure
increase at each planet turned
out to be the same, but Mars lost
ten times as many oxygen ions as
Earth did – enough to account for
the differences in atmosphere
between the two planets.
The current combination of
increased solar activity and the
array of European planetary
orbiters in place mean that
further alignments are possible,
including similar studies at
Venus.
http://www.esa.int
GEMS now InSight
A proposed mission to examine
the interior of Mars has
changed its name from GEMS
(Geophysical Monitoring Station)
to InSight, standing for Interior
Exploration using Seismic
Investigations, Geodesy and Heat
Transport. InSight is one of three
suggested Discovery missions
currently being considered for
flight by NASA. This mission
would offer the first chance
to find out about the internal
structure of another planet.
http://www.insight.jpl.nasa.gov
2.10
was the instrument used to find this
species in gaseous form; the spectral signature of the solid form is
distinctive. The Spitzer data came
from XX Ophiuchi, a binary system
6500 light-years from Earth, suspected of having a lot of dust in the
immediate environment. Nye Evans
of Keele University, lead author of
a paper in Monthly Notices of the
RAS, was looking for silicate dust
but found C60. The existence of C60
in solid form implies that there must
be plenty of C60 around XX Ophiuchi – perhaps as much as 10 000
times the volume of Mt Everest.
http://www.keele.ac.uk
Black hole wind
breaks record
Winds moving at 3% of the speed
of light have been detected from a
stellar-mass black hole (IGR J170913624) using data from NASA’s
Chandra X-ray observatory. The
wind speed matches some of the fastest winds generated by black holes
millions or billions of times more
massive. The wind is not limited
to a jet, but blows in all directions
out from the black hole. And it is
intermittent. The wind speed was
calculated using Chandra spectroscopic data; two months before these
observations, similar data showed no
extreme speeds.
Simultaneous observations made
with the National Radio Astronomy Observatory’s Expanded Very
Large Array showed that a radio jet
from the black hole was not present
when the ultra-fast wind was seen,
although a radio jet is seen at other
times. This agrees with observations
of other stellar-mass black holes,
suggesting that the production of
winds can stifle jets.
Another unanticipated finding is
that the wind, which comes from
a disc of gas surrounding the black
hole, may be carrying away more
material than the black hole is capturing – up to 95% of the matter in
the disc.
http://tinyurl.com/chandrawind
LRO maps recent
lunar tectonics
High-resolution images from
NASA’s Lunar Reconnaissance
Orbiter (LRO) spacecraft are allowing researchers to map deformation
of the Moon’s crust over the past
50 million years – the recent past,
geologically speaking. What they
have found is evidence of extension,
surprising when the Moon is considered to be contracting overall as it
continues cooling after its formation
4500 million years ago.
The LRO Camera shows small
linear trench-shaped valleys, much
longer than they are wide, with flat
floors. On Earth such features are
known as graben and occur when the
crust is extending on faults that form
the long valley sides. The floor drops
between the faults to give the characteristic grave-like shape. On the
Moon, the broadest graben is about
500 m wide and the drop is 20 m –
not large features, but significant.
Their existence means that, despite
the overall contraction associated
with its continuing cooling, parts
of the Moon are extending. In other
words, the cooling contraction cannot be strong – it is weak enough to
be overcome locally by extension.
This weak cooling contraction suggests that the Moon did not completely melt when it formed.
The research was published in the
March 2012 issue of Nature Geoscience.
http://tinyurl.com/LROcrust
Surprisingly fast
lunar impactors
Lunar Reconnaissance Orbiter data
(from the Lunar Orbiter Laser Altimeter) suggest that the pulse of impacts
on the Moon around 4000 million
years ago – the Late Heavy Bombardment or lunar cataclysm – involved
bolides moving more quickly than
those before or since. This supports
models of solar system evolution
that invoke major migrations of the
giant planets at this time, disrupting
minor solar system bodies and sending them towards the inner planets.
The Nectaris impact basin, near
the Apollo 16 landing site, is used
as a marker in this study. Digital
maps of the lunar surface show that
craters near the 860 km diameter
Nectaris impact basin were 30 to
40% larger on average than those in
comparable populations with older
craters. The research team suggests
that the craters were formed by projectiles hitting twice as fast as those
found on more ancient terrains. The
inferred increase in velocity seems
to have occurred after the formation
of the Moon’s largest impact basin,
the 2500 km diameter South Pole–
Aitken Basin. Most of the craters
formed in this region involve lowvelocity impactors. The fast impactors also seem to have hit the Moon
before the formation of the largest
lava-filled impact basins on the
lunar nearside, the mare. The Nectaris basin appears to have formed
at around the start of the lunar cataclysm.
Simone Marchi, of the University
of Nice Sophia Antipolis, Southwest
Research Institute, University of
Boulder and the Lunar and Planetary
Center in Houston, Texas, is lead
author on the publication in Earth
and Planetary Science Letters.
http://lunarscience.arc.nasa.gov
HST finds new
planet type
Data from the Hubble Space Telescope have confirmed that a superEarth exoplanet, GJ1214b, is mostly
water, with a steamy atmosphere
and an exotic water-rich interior.
No planets known so far have such a
water-rich composition.
GJ1214b was discovered in 2009
by the ground-based MEarth project led by David Charbonneau. It
has a diameter about 2.7 times that
of Earth and a mass of seven times
Earth’s, giving it a surprisingly low
density of about 2 g cm –3. The planet
was also found to have a hazy atmo­
sphere.
Now Zachory Berta of the Harvard-Smithsonian Center for Astrophysics and colleagues have used the
Wide Field Camera3 on the HST to
examine the infrared spectrum of the
planet’s atmosphere, using light from
its host star. This was, in part, to see
through the hazes thought to limit
observations of GJ1214b, because
hazes are more transparent to IR
light than to visible light. Berta and
colleagues found that the atmosphere
was featureless over a wide range of
wavelengths. The atmospheric model
most consistent with these data is a
dense atmosphere of water vapour.
This planet orbits a red dwarf star
with a period of 38 hours, at a distance of 2 million kilometres, giving
it a temperature estimated at 500 K.
The density of the planet suggests
that, as well as a dense water atmo­
sphere, it has an unusual interior.
The density of 2 g cm–3 , between that
of ice (1 g cm –3) and rock (typically
2.5–3 g cm –3, although Earth’s density is 5.5 g cm –3 on average) suggests
an interior made of exotic materials such as “hot ice” or “superfluid
water”.
A theory of planet formation suggests that such a planet formed in the
outer parts of a stellar nebula, where
water ice was plentiful. It must then
have migrated inwards, possibly
spending time in the habitable zone
of its star, at temperatures where
water would be liquid at its surface. GJ1214b is in the constellation
Ophiuchus, just 40 light-years away,
making it a prime target for observations with the James Webb Space
Telescope, the planned replacement
for the Hubble Space Telescope from
NASA, ESA and the Canadian Space
Agency.
Berta et al. published their results
in The Astrophysical Journal.
http://www.spacetelescope.org
A&G • April 2012 • Vol. 53