Mission update
Mineralogical
map of Vesta
The visible and infrared spectrometer on NASA’s Dawn mission
has mapped out variations in the
composition of silicate minerals
on the southern hemisphere of the
asteroid Vesta.
The map is colour-coded so that
areas with the silicate mineral
pyroxene that is rich in purple
have more magnesium, whereas
those coloured yellow have pyroxenes richer in iron.
Meteorites with these mineralogical compositions (called diogenites and eucrites respectively)
have been confirmed to come from
Vesta by the Dawn mission, along
with the howardite meteorites.
Identifying the source of what
are collectively called the HED
meteorites makes the asteroid one
of the largest single sources for
Earth’s meteorites.
Vesta is a planetary relic formed
early in the life of the solar system
– a layered, planetary building
block with an iron core, formed
4.55 million years ago. Dawn has
also shown surprisingly steep
topography on Vesta, making
landslides more likely, and the
body shows significant differences
Spitzer spots
super-Earth
NASA’s Spitzer Space Telescope has
detected the infrared light from an
exoplanet, 55 Cancri e, a body about
twice the size and eight times as massive as Earth. Spitzer was also the
first instrument to detect light from
another planet, a hot Jupiter in 2005.
Spitzer researchers compared the
spectrum of the parent star alone
to that of the star plus the planet,
to determine emission from the
planet alone. In order to extend
the technique from gas giant planets to super-Earths, the Spitzer
team changed the way the observatory worked, including altering the
cycling of a heater, for example, to
boost precision.
The super-Earth orbits its star
every 18 hours, and is tidally locked.
The planet’s density suggests that it
is a watery world and Spitzer’s IR
data suggest that the sunward side
A&G • June 2012 • Vol. 53 News • Mission Update
Space Shorts
JUICE for Jupiter
The first Large-class mission of
ESA’s Cosmic Vision 2015–2025
programme will be a mission
to the icy moons of Jupiter,
expected to be launched in 2022.
The less-than-enticingly named
JUICE (Jupiter Icy moons
Explorer) will take a closer
look at the moons Callisto
and Europa, thought to have
a subsurface ocean, before
orbiting Ganymede, the only
moon with its own magnetic
field. The mission will address
two key themes of Cosmic
Vision: what are the conditions
for planet formation and the
emergence of life, and how does
the solar system work?
http://bit.ly/IWR1q9
As and Se in old star
1: The southern hemisphere of asteroid Vesta, showing variations in its
silicate minerals. (NASA/JPL-Caltech/UCLA/INAF/MPS/DLR/IDA)
from Earth’s Moon. The two
largest impact craters, for example, are relatively young, with
Veneneia forming approximately
2 billion years ago and the Rheasilvia basin about 1 billion years ago.
Vesta also bears similarities to
has a temperature of around 2000 K.
Such a high temperature suggests
that the planet does not have much
of an atmosphere, because atmospheric circulation would dissipate
heat. “It could be very similar to
Neptune, if you pulled Neptune
in toward our Sun and watched its
atmosphere boil away,” said Michaël
Gillon of Université de Liège in Belgium, principal investigator of the
research, which appears in The
Astrophysical Journal.
http://www.nasa.gov/spitzer
Dunes move
across Mars
Researchers using the HiRISE camera on NASA’s Mars Reconnaissance
Orbiter have quantified the movement of sand in dune fields on Mars
– and found parts of the planet where
it takes place at about the same rate
as on Earth.
Mars has extensive dune fields that
other low-gravity worlds such as
Saturn’s small icy moons, and its
surface has light and dark markings that do not match the patterns
on Earth’s Moon.
http://www.nasa.gov/dawn
http://dawn.jpl.nasa.gov
indicate the directions of wind flow,
but it had not been clear whether the
dunes were actively moving across
the surface, or static “fossil” dunes.
Now, HiRISE images from the past
two years indicate that entire dunes
as much as 60 m thick are moving as
coherent units across Mars. This is
unexpected because the density of
the martian atmosphere is about 1%
that of Earth and high-speed winds
are both rarer and weaker.
The team worked on images of the
Nili Patera region of Mars, tracking
small ripples that move on the surface of big sand dunes, using software developed at the California
Institute of Technology (Caltech) in
Pasadena. The small ripples move
in ways related to the migration of
the dunes as a whole and the pattern
measured between 2007 and 2011
indicates that these martian dunes
are active. In addition, the volume of
sand moving in this region is about
2 m3 m –1, similar to the flux on Earth
in places such as Antarctica. This
Arsenic and selenium (plus
cadmium, tellurium and
platinum) have been found
outside the solar system for
the first time, in a 12 billionyear-old star called HD 160617.
Researchers used ultraviolet
spectroscopy from the Hubble
Space Telescope public archives.
The team also examined data for
this star from the public archives
of several ground-based
telescopes and were able to
detect 45 elements in total. The
significance of these elements
is that they formed in the
r-process, during supernovae
and so predate the formation of
this star. The r-process involves
conditions so extreme it cannot
be replicated in the lab, leaving
astronomical data as the best
source of information.
https://carnegiescience.edu/news/
old_star_new_trick
Many rogue planets?
A team led by Chandra
Wickramasinghe has suggested
that primordial planets formed
300 000 years after the Big Bang
might be much more abundant
than thought, numbering around
1014 in our galaxy, and could not
only account for the missing
baryonic dark matter, but also
provide a mechanism for the
spread of life in accordance with
the theory of panspermia. The
team assumes that primordial
giant planets lose their haloes
of gas but keep differentiated
rocky cores and can harbour
life. The research is published in
Astrophysics and Space Science.
http://www.springerlink.com/
content/0004-640x
3.7
News • Mission Update
implies a similar rate of weathering
to Antarctica and establishes the
wind as a significant element of erosion on Mars.
The data were published in Nature
on 9 May by Nathan Bridges of
Johns Hopkins University Applied
Physics Laboratory, and co-authors.
researchers analysing stable isotope
data from the moon’s atmosphere
obtained by NASA’s Cassini mission.
The atmospheric methane is
thought to have originated in an episode of outgassing from the moon,
perhaps as a result of restructuring
of Titan’s interior as heavier mat­
eri­als sank towards the centre and
lighter ones rose. Conor Nixon of
the University of Maryland, College
Park, and colleagues used spectra of
methane from Cassini’s composite
infrared spectrometer to estimate
how much “heavy” methane containing 13C is present in Titan’s
atmosphere. Reactions involving
methane in the moon’s atmosphere
fractionate methane containing the
two stable isotopes, so that the concentration of heavier methane in the
atmosphere increases the longer it
spends in the atmosphere.
This age estimate includes the
assumption that no methane escapes
from the top of the atmosphere. If
escape is included, the current methane may have existed in the atmo­
sphere for only 10 million years. And
if the methane is being replenished by
clathrates or cryovolcanoes on the
planet, the model is not valid.
The research is published in two
papers in The Astrophysical Journal,
(C A Nixon et al.; K E Mandt et al.)
http://www.nasa.gov/mro
IBEX data deny
bow shock
The bow shock, a region of plasma
that abruptly changes density ahead
of the heliopause, does not exist,
suggest results from NASA’s Interstellar Boundary Explorer (IBEX)
spacecraft.
The bow shock is effectively a
shock wave, the equivalent of the
sonic boom that forms in Earth’s
atmosphere when an object moves
at the speed of sound. A bow shock
surrounds Earth’s magnetosphere as
it meets the solar field. But the heliosphere itself does not seem to have
its own shock. The problem seems to
lie in the relative speed of the heliosphere and interstellar space. The
IBEX data suggest that the relative
speed of the two – 85 000 km per
hour – is too slow. It is more of a bow
wave ahead of a boat than a sonic
boom, according to David McComas
of the Space Science and Engineering
Division at Southwest Research Institute, who is principal investigator of
the IBEX mission. In addition, the
magnetic pressure in the interstellar medium is higher than had been
thought, which would require even
higher relative speeds to form a bow
shock. McComas and team published the results in Science Express.
http://bit.ly/J3YEht
Lunar missions
seek payloads
The race for the $30m Google Lunar
X PRIZE is creating science opportunities for European lunar researchers. Four teams competing for the
competition presented their plans at
the European Lunar Symposium in
Berlin in April. Representatives from
Hungary’s Team Puli, Italy’s AMALIA mission, and European members
of Team FREDNET and Synergy
Moon invited the 170 lunar scientists attending the meeting to come
up with science payloads that could
be carried by their rovers and landers.
The Google Lunar X PRIZE challenges a privately funded team to
place a robot on the Moon’s surface,
explore at least 500 m and transmit
high-definition video and images
back to Earth. The first team to do
so wins a $20m prize, while the second team will earn $5m. The Google
3.8
http://bit.ly/IPfQaB
http://bit.ly/LIl45Z
Happy 25th birthday JCMT Old method finds
The James Clerk Maxwell Telescope (JCMT) on Mauna Kea in Hawaii,
saw first light in 1987 and continues to lead in submillimetre astronomy
with SCUBA-2. The JCMT, at 15 m diameter, is the largest dish in the
world dedicated to observing at submillimetre wavelengths from the
coldest and most distant material in the universe and has been a very
successful instrument. One of the reasons for this success is the series
of increasingly sensitive instruments that have been used. An early
instrument called UKT14 revealed young stars at the very earliest
stages of their formation, the Class 0 protostars. The world’s first
sub-mm imaging camera, SCUBA, operated on the JCMT for eight years
and enabled the discovery of a previously unknown population of dusty
galaxies (SCUBA galaxies) and produced the first ever images of cold
debris discs around nearby stars, which may indicate the presence of
planetary systems. Now SCUBA-2 continues the tradition, as shown in
this image of galaxy M66 in which the 850 µm radiation from cool dust
lanes is shown in red against the visible galaxy. There is an unusual
compact cloud in the southern part of the galaxy that is a likely site for
future star formation. (VLT/ESO, JAC, G Bendo)
http://outreach.jach.hawaii.edu
Lunar X PRIZE is one of three active
competitions from the X PRIZE
Foundation, a non-profit organization that creates and manages global,
incentivized competitions.
Plans presented at the meeting by
the teams highlighted the range and
innovation of the teams’ approaches
to the lunar challenge. Designs for
rovers included a mast carrying
stereo cameras from Team Italia, a
spike-wheeled locomotion system by
Team Puli and a spherical rover by
FREDNET that propels itself along
through displacement of ballast.
http://www.googlelunarxprize.org
Titan’s methane
maybe very old
Methane in the atmosphere of Saturn’s moon Titan was formed up to
1600 million years ago, according to
new exoplanet
French mathematician Urbain Le
Verrier predicted the existence of
Neptune on the basis of perturbations in the motion of Uranus, 150
years ago. Now the same method has
been used to infer the presence of an
exoplanet, the first success of this
technique outside the solar system.
The new planet was found as a
result of the Hunt for the Exomoons
with Kepler (HEK) project, in which
a team led by David Nesvorny of
Southwest Research Institute analysed recently released Kepler data
to identify systems with transiting
planets that show transit variations
indicative of hidden companions.
The Sun-like star known as KOI872 proved exceptional in that it has
transits with remarkable time variations over two hours. The HEK team
used Le Verrier’s techniques to speed
up the calculations and showed that
the observed variations can be best
explained by an unseen planet about
the mass of Saturn that orbits the
host star every 57 days. According to
the analysis, the planetary orbits are
very nearly coplanar and circular,
like the orbits in our solar system.
http://swri.org/press/2012/unseenplanet.htm
A&G • June 2012 • Vol. 53