Download HST reveals upheaval in Jupiter`s clouds

News • Mission Update
Space Shorts
Joining the jet set
A neutron star with an extended
X-ray jet has been detected by
the Chandra X-ray Observatory.
The jet comes from Circinus X‑1,
a binary system where a
neutron star orbits a star a few
times the mass of the Sun,
some 20 000 light-years from
Earth. Such jets are normally
associated with black holes,
so this discovery should clarify
which features of superdense
stars are required to form jets.
“Gravity appears to be the key
to creating these jets, not some
trick of the event horizon,” said
Sebastian Heinz of the University
of Wisconsin at Madison, who led
the study. The X-ray jets of highenergy particles are powerful
enough to create and maintain
“balloons” of gas that cause the
diffuse lobes of radio emission
previously detected around
Circinus X‑1. These results will
appear in Astrophysical Journal
Letters.
http://chandra.harvard.edu http://chandra.nasa.gov Moon’s suitcase science
The next stage of NASA’s lunar
exploration is taking shape, with
the selection of seven proposals
in the Lunar Sortie Science
Opportunity Programme, plus
two new programmes based
in NASA’s Planetary Science
Division. The LSSP options target
geophysical measurements and
communications, in the form of
“suitcase science”: autonomous
packages suitable for the lunar
surface. Proposals include
examining the regolith and lunar
radiation environment as well
as seismology and heatflow. It is
hoped that development of these
instruments will bring wider
research benefits.
http://www.nasa.gov/exploration
Saturn: more live moons
Cassini continues to discover
more about Saturn and its
moons, now finding that two
more of them, Tethys and Dione,
emit plasma. This suggests
that there may be some sort
of geologic or even volcanic
activity on these moons as well
as on Titan and Enceladus, the
other active moons of Saturn.
Further investigations combining
observations from different
Cassini instruments should bring
a better understanding of these
moons and their properties.
http://www.nasa.gov/cassini
4.8
Mission update
HST reveals upheaval in Jupiter’s clouds
A rapid transformation in the shape and colour of cloud belts on Jupiter has been observed by scientists using the
Hubble Space Telescope. The distinctive belts of cloud encircling Jupiter are constantly changing, but there has
been much more rapid and significant change in some of the cloud belts between March and June this year. The
images (from 25 March, left, and 5 June, right) show the changes: a white cloud layer, usually signifying highaltitude cloud, has disappeared and a brown band, typically signifying cloud from lower levels, has taken its place.
This suggests that higher cloud has merged with the deeper layers. Also there has been a change in the patterns
of cloud within cloud bands, and the appearance of a snake-like dark streak that may be a rift in the cloud layers,
allowing views of the deeper parts of the atmosphere. Although this is the third time Jupiter’s bands have been
spotted changing so extensively over such a short time, this is the first time the high-resolution HST has observed
the transformation. It is hoped that the detail available in these images will help researchers to understand
the underlying atmo­spheric processes. (NASA, ESA, A Simon-Miller [NASA Goddard Space Flight Center], A
Sánchez-Lavega, R Hueso, and S Pérez-Hoyos [University of the Basque Country], E García-Melendo [Esteve Duran
Observatory Foundation, Spain], and G Orton [Jet Propulsion Laboratory])
New technique
for exoplanets
Observers at the European Southern
Observatory have found a way to distinguish planets or companion stars
from artefacts of the observing process in binary and planetary systems.
Spectral deconvolution, carried out
with SINFONI on ESO’s VLT, identifies real bodies because their apparent
position does not vary when observed
with different parts of the spectrum.
The problem with looking for
extrasolar planets and low-mass or
brown-dwarf stars is that they are so
dull. The bright light of the principal
star dominates, with the result that
direct observations of such bodies
are hard to separate from unusual
features of the star itself or artefacts
of the telescope and instruments. But
the positions of such features tend to
vary with the wavelength in which
they are observed, unlike the positions of any companions: real bodies
appear in the same place, whatever
the wavelength. So observers can use
an imaging spectrograph to pick out
companions that are otherwise indistinguishable.
SINFONI allowed Niranjan Thatte
and his colleagues at ESO to examine a companion at a distance of
3 AU from AB Doradus C, without
including light from the host star.
The data suggest a higher temperature for the companion star, which
had been considered unusually cool.
It now appears that this brown dwarf
is at about 3000 K, slowly heating up
exactly as expected in theory for a
star of 9% of the Sun’s mass.
http://www.eso.org
Make a black
hole? Impossible
Physicsts may have solved the information-loss paradox associated with
black holes, with the result, they say,
that black holes cannot form under
current conditions and all black holes
formed at the beginning of time.
Tanmay Vachaspati, Dejan Stojko­vic
and Lawrence Krauss of Case West-
ern Reserve University, Ohio, US,
examined what happens when matter
collapses into a black hole. If all information about the collapsing matter
is lost, it defies the laws of quantum
physics. Yet, in current thinking, that
is exactly what does happen. The
researchers calculated how a black
hole might form, and concluded that,
because information about the collapsing mass escapes in the form of
non-thermal radiation known as preHawking radiation, it can’t form a
black hole. The mass shrinks, but never
quite collapses inside an event horizon
because pre-Hawking radiation allows
information about the nature of what
is collapsing to be recovered far from
the collapsing mass. According to the
researchers, if black holes did indeed
form, information from the initial state
would disappear in a burst of thermal
radiation, carrying no information
about its initial state.
This work does not impinge upon
observations or the gravitational
effects of black holes. What is controversial about the new finding is
that “from an external viewer’s point
of view it takes an infinite amount of
A&G • August 2007 • Vol. 48
News • Mission Update
Mars rover poised to descend into giant crater
Is this the structure of a large impact crater on Mars? This outcrop of
bedded rocks photographed by the Mars Exploration Rover Opportunity at
Cape St Vincent, may show effects of the impact that formed Victoria Crater
a few million years ago. The pale, continuous layered rocks found all round
the crater rim may represent the surface rocks of Mars before the impact.
The less consolidated rubbly rocks above may have been deposited in the
impact, which left the former surface layers tilted upwards towards the
crater rim. (NASA/JPL/Cornell)
NASA’s veteran Mars Exploration
Rovers are still at work, their tracks
observed by the HiRISE cameras on
the Mars Reconnaissance Orbiter,
some three years after they landed.
Opportunity is heading into an
impact crater in search of older
rocks, and Spirit, despite a jammed
wheel, has found silica-rich soil
that may signal the presence of
water when it was formed.
Spirit found this unusual soil in
part thanks to its stuck wheel. As
the rover moves, the faulty wheel
gouges out a track in the martian
dust. Most of the bright soil that has
been found in this way proves rich
in sulphur, but in this case the bright
patch, some 8 cm wide, turned out
to be 90% silica, measured with
Spirit’s X-ray spectrometer. Unlike
time to form an event horizon and
that the clock for the objects falling
into the black hole appears to slow
down to zero”, said Krauss. Stojkovic added: “In fact, since in quantum
mechanics the observer plays such an
important role in measurement, the
question of formation of an event
horizon is much more subtle.”
This research is accepted for publication in Physical Review D.
A&G • August 2007 • Vol. 48 quartz sand on Earth, however, this
silica-rich soil is not crystalline; it
may have formed in a hot spring, or
from the interaction of acidic steam
from volcanoes with soil.
Opportunity will descend into
Victoria Crater, 6 km from its
landing site, to examine the layered
rocks exposed in its walls. This
is an impact crater nearly 800 m
across, much larger than Endurance Crater, which Opportunity
explored in 2004. Victoria Crater
exposes deeper – and therefore
older – rocks, allowing Opportunity to extend its search for signs of
wetter climates on Mars in the past.
The descent is, however, a calculated risk; Opportunity has spent
nine months exploring a quarter of
the circumference in search of the
Spot the centre
of the Earth
The constantly changing shape and
distribution of mass of the Earth
makes pinning down its centre of
mass a tricky business. But those
same constant changes make a reference point of this type increasingly
The tracks of rover Opportunity from its arrival at Duck Bay (left), around
the scalloped rim of the crater and then back to Duck Bay to start its
descent, taken by the HiRISE camera on NASA’s Mars Reconnaissance
Orbiter spacecraft. (NASA/JPL/Univ. of Arizona)
best descent route. The chosen path,
via Duck Bay where Opportunity
arrived at the crater, has a 15°–20°
slope that the rover should be able
to descend and ascend provided all
its wheels keep working. The other
rover has a stuck wheel. Mission
planners hope Opportunity will
visit the crater, and carry on exploring elsewhere, but they feel the risk
of it remaining in the crater is worth
important for understanding our
planet. Now NASA has produced a
better reference frame and location.
Donald Argus of the Jet Propulsion
Laboratory can pinpoint the centre
of mass of the solid Earth – excluding seasonal changes in oceans and
atmosphere – to within 1 mm a year,
a great improvement. His method
involves combining four space-based
techniques to assess the precise posi-
the chance of failure, given the value
of the observations available there,
especially at this stage of the mission. Given that their design lifetime
was 90 days, the MER engineers
accept that the rovers may fail, and
there have indeed been problems
that limit their usefulness, but Spirit
and Opportunity keep on going.
http://www.nasa.gov/mission_pages/
mer/index.html
tions of sites on the Earth’s surface,
which then allow estimation of the
position and movement in space of
the centre of mass. This method, published in Geophysics Journal International, will refine measurements of
such phenomena as rising sea level,
glacial rebound, tectonic movements
and volcanic eruptions.
http://www.earth.nasa.gov/history/lageos/
lageos.html
4.9