Mission update
Did Mars have a
global wet era?
Minerals suggesting wet conditions
4 billion years ago on Mars have
been found more frequently in the
southern martian hemisphere, leading to suggestions that the planet had
a wet and a dry hemisphere. But now
similar minerals have been found
exposed in craters in the north, suggesting global watery conditions.
The minerals found are phyllosilicates, hydrated clay minerals that are
strong indicators of wet rock-forming
conditions. The OMEGA instrument
on ESA’s Mars Express orbiter picked
out the characteristic elemental abundance pattern of relatively high iron
and magnesium, but low aluminium,
indicating these hydrated silicates, at
thousands of small outcrops in the
southern hemisphere, in ancient
sediments. The northern half of
Mars was thought not to have experienced the same conditions, because
comparable outcrops had not been
found. But the northern hemisphere
is blanketed with younger rocks,
mainly lava flows. Mars Express
data, together with higher resolution information from NASA’s Mars
Reconnaissance Orbiter, now show
comparable signals from craters in
the northern hemisphere that reveal
deeper – and older – rocks.
At least nine out of 91 craters targeted contained the phyllosilicates.
So it is likely that the warmer and
wetter conditions inferred for the
presence of these minerals existed
across the whole of Mars some 4 billion years ago – so conditions favourable for the formation of life may
have spread over the whole planet.
However, it is not very clear how
long the relatively balmy conditions
lasted – OMEGA data also suggest
that the mineral olivine is present in
locations very close to the phyllosilicates. If water were abundant and
present for a long time, olivine would
not survive, so the wet phase may
have been short or intermittent.
http://www.esa.int/esaSC/
SEMU70MZLAG_index_0.html
Instruments for
Pluto pass tests
NASA’s New Horizons probe is now
more than half way to dwarf planet
Pluto and has concluded a series of
instrumental tests ready for its close
A&G • August 2010 • Vol. 51 News • Mission Update
Space Shorts
Deep Impact departs
The NASA spacecraft Deep
Impact made its last Earth
flyby on 27 June on its way to
a close encounter with comet
Hartley 2 in November. The
gravity assist of this fifth and
final pass was used to alter the
spacecraft’s trajectory to reach
its target. Hartley 2 is a goal for
the EPOXI extended mission
for Deep Impact, which made
headlines when it sent a probe
crashing into comet Tempel 1 in
2005. Deep Impact will not hit
Hartley 2, but will collect data
with its digital colour cameras
and infrared spectroscopy.
http://epoxi.umd.edu
http://www.nasa.gov/epoxi
India goes for TMT
The Thirty Metre Telescope
Project has gained another
member, with India signing up
as an observer, the first step
towards full involvement and a
significant statement of scientific
intent for India. “The government
and people of India recognize
the importance of embarking
on world-class, international
science collaborations,” said
Thirumalachari Ramasami,
Secretary of the Dept of Science
and Technology. “The Thirty
Meter Telescope will enable
us to continue and expand our
role as an international leader
in technology development and
fundamental research.” The TMT,
to be built on Mauna Kea, Hawaii,
is scheduled to begin scientific
operations in 2018 as the first of
the next generation of groundbased optical observatories.
http://www.tmt.org
Kepler data release
This image of Mars southwest of the Tharsis volcanic region (with north
at the top of the image) shows a plateau made of pale rocky mounds or
rock fragments around 2 km high, as well as linear features thought to
be faults trending northwest–southeast. The origin of the mounds is
not clear. The image, which comes from just south of Magellan Crater
whose rim can just be seen at the northern (right hand) side, covers an
area of 190 × 112 km at a resolution of 25 m per pixel, and was taken by
the Mars Express High-Resolution Stereo Camera (HRSC). The rocky
mounds or fragments might represent rock shattered by an impact, or
they might result from groundwater melting and removing subsurface
rock (a martian process called subrosion) as a result of rising magma
melting frozen volatiles in the subsurface. The honeycomb of cavities
thus formed then collapse, leaving a broken surface. The linear features
– deep, well-defined valleys – are thought to have formed along the lines
of faults that moved during an impact or as a result of volcanic activity in
the nearby Tharsis region. (ESA/DLR/FU Berlin: G Neukum)
Another 43 days of data from
NASA’s Kepler mission has been
released, allowing the search
for Earth-like planets to cover
another 156 000 stars. Kepler
uses photometry to pick up
the fluctuations in brightness
caused by planets orbiting other
stars, combining these data with
observations from ground-based
telescopes and the Hubble and
Spitzer Space Telescopes to rule
out binary stars – whose light
also fluctuates – and determine
the size of putative planets.
The repeated measurements
required to be sure of identifying
a planet like Earth orbiting in the
habitable zone of a Sun-like star
will take about three years.
http://www.esa.int/esaSC/SEMZ1FOZVAG_index_0.html
http://www.nasa.gov/kepler
Mystery mounds on Mars
4.9
News • Mission Update
VISTA unveils Sculptor Galaxy
The European Southern Observatory’s new UK-designed and built VISTA
telescope is now conducting its first observing campaign. This image
of the Sculptor Galaxy shows off the capabilities of this world-record
instrument: with a mirror over 4 m in diameter, it is the largest survey
telescope yet built. The Sculptor Galaxy was discovered by Caroline
Herschel in 1783 and, while it is visible with binoculars, it is very dusty.
VISTA, at infrared wavelengths, can see through the dust to the intense
star-formation within. The image shows the galaxy (13 million light-
approach in 2015. New Horizons carries LORRI, the Long-Range Reconnaissance Imager, one of the largest
interplanetary telescopes ever flown,
to take a close look at the surface.
LORRI will be able to resolve objects
the size of a football field on Pluto
and will be used together with Ralph,
a visible and infrared spectrometer.
Mission scientists hope to be able to
detect hazes, geysers from cryptovolcanism, or even streaks as found
on Neptune’s moon Triton. Alice is
a UV imaging spectrometer that will
examine the absorption of sunlight
through Pluto’s atmosphere as New
Horizons moves into its shadow. The
Radio Science Experiment will do the
same for radio signals from NASA’s
Deep Space Network, to determine
more about the pressure and thickness of Pluto’s atmosphere.
http://pluto.jhuapl.edu
Mystery flash
on Jupiter
A flash of light seen on Jupiter on 3
June came from a giant meteor burning up high above Jupiter’s cloud tops,
according to observations made with
the Hubble Space Telescope. But this
jovian impact did not leave behind
the localized dark debris clouds seen
in previous collisions.
Australian amateur astronomer
Anthony Wesley saw a two-secondlong flash of light at 4:31 p.m. (EDT)
on 3 June, while watching a live video
feed of Jupiter from his telescope. In
the Philippines, amateur astronomer
4.10
years away) almost edge on, with spiral arms clearly visible and a bright
core, plus many cooler stars that are barely detectable in visible light.
Astronomers will also use VISTA to examine the numerous cool red giant
stars in the Sculptor Galaxy halo, to measure the composition of some of
the small dwarf satellite galaxies, and to search for new objects such as
globular clusters and ultra-compact dwarf galaxies through the dust.
(ESO/J Emerson/VISTA/Cambridge Astronomical Survey Unit)
http://www.eso.org/public/teles-instr/surveytelescopes/vista
happen as frequently as every few
weeks, but it is only a guess. The fact
that these flashes can be observed
from Earth means astronomers have
a new capability that can be exploited
with increased monitoring of Jupiter
and the other planets.
http://hubblesite.org/news/2010/20
Pan-STARRS 1
up and running
1: The PS1 Observatory on Haleakala, Maui, just before sunrise, with Mauna
Kea in the background. Visible through the dome shutter are the calibration
screen, the secondary mirror baffle, the truss and the primary mirror
covers. (Rob Ratkowski)
Chris Go confirmed that he had
simultaneously recorded the transitory event on video. A flash of light
bright enough to be seen 400 million
miles away suggests an impact, but
this must differ from previous examples because it did not leave the persistent debris in Jupiter’s atmosphere
seen after the impact of comet Shoemaker-Levy, for example.
The HST Wide Field Camera 3 took
images on 7 June that show no sign of
debris above Jupiter’s cloud tops, so
the object didn’t descend beneath the
clouds and explode as a fireball. An
explosion would have produced dark
sooty blast debris that would have
rained down onto the cloud tops. The
impact site would have appeared dark
in the ultraviolet and visible images,
and it did not. So there was no
explosion generating a giant plume
in Jupiter’s atmosphere. The flash of
light was caused by the same physics
behind a meteor on Earth. A shock
wave generated by ram pressure as
the meteor speeds into the planet’s
atmosphere heats the impacting body
to a very high temperature, and as
the hot object streaks through the
atmosphere it leaves behind a glowing trail of superheated atmospheric
gases and vaporized meteor material
that rapidly cools and fades in just a
few seconds.
Though astronomers are largely
uncertain about the rate of large
meteoroid impacts on the planets,
the best guess for Jupiter is that
the smallest detectable events may
The first 1.8 m Pan-STARRS tele­
scope, including the world’s largest
digital camera, is now operational
on Haleakala, Hawaii (figure 1). PS1
will use the 1400-megapixel camera
to scan the skies each night, looking
for objects that have moved. Its goal
is to match the asteroids it finds to
those already catalogued, add more
to the tally and, especially, find any
likely to come near Earth, with the
possibility of collision. In the next
three years, PS1 is expected to discover around 100 000 asteroids, as
well as cataloguing 5 billion stars
and 500 million galaxies. Each
night’s observing will involve 500
exposures and 4 Tb of data. PS1 is
the experimental prototype for the
larger PS4 telescope, which will have
four times the power of PS1 and is
planned for Mauna Kea. PS1 is now
run by the PS1 Science Consortium,
a group of 10 funding institutions,
including UH Manoa, in the United
States, Germany, United Kingdom
and Taiwan.
http://www.ifa.hawaii.edu/info/pressreleases/PS1
A&G • August 2010 • Vol. 51