Download Sledging on Mars

News • Mission Update
Space Shorts
Euclid moving forward
Europe’s mission to understand
the accelerating expansion
of the universe has come
a step closer with ESA’s
announcement that Astrium in
Toulouse, France, will deliver
the integrated payload module
and Thales will be prime
construction contractor. Eight
UK institutions have agreed
grants worth £8.5 million
from the UKSA to develop
instruments and support
development of data processing
capabilities. The Mullard Space
Science Laboratory is leading
the development of the main
camera and the Open University
will carry out radiation testing
and verification. A key Science
Data Centre will be set up in
Edinburgh.
http://sci.esa.int/euclid
Japan favours TMT
The Thirty Meter Telescope
(TMT) project has gained the
support of Japan, which has
agreed funding worth about
$12m for preparatory work and
construction. TMT consists of
492 mirrors that combine to form
the 30 m primary mirror. Japan
is expected to manufacture the
main telescope structure and the
mirror blanks, as well as provide
a portion of the polishing of the
mirrors and instrumentation.
Japan is expected to contribute
a quarter of the total cost. The
TMT should begin science
observations in 2022 on Mauna
Kea, Hawaii.
http://tmt.org
IRIS launched
A power cut at Vandenberg Air
Force Base in California delayed
the launch of NASA’s Interface
Region Imaging Spectrograph
(IRIS) mission until 27 June.
That launch was unusual: the
Pegasus XL rocket carrying IRIS
was deployed from an aircraft
over the Pacific Ocean at an
altitude of 12 km, after which
the rocket placed IRIS into a
Sun-synchronous polar orbit
that will allow it to make almost
continuous solar observations
during its two-year mission.
IRIS is a NASA Explorer Mission
to observe how solar material
moves, gathers energy and
heats up as it travels through
the interface between the Sun’s
photosphere and corona.
http://1.usa.gov/12C1hiz
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Mission update
Sledging on Mars
Linear gullies on martian sand
dunes may be the work of chunks
of carbon dioxide – dry ice – sliding
down the sediment surface
like miniature hovercraft, then
sublimating to leave only an empty
pit at the base. Many surface
processes leave evidence behind
in the form of a gully or channel;
these gullies have a roughly
constant width of a few metres,
with raised banks (levees) on each
side. Fluid flow generally carries
material downwards, carving out a
channel and leaving a fan-shaped
apron of debris at the bottom. But
these gullies appear to have been
carved by a solid object pushing
sediment up at the sides; the
debris fan is also missing. Images
from MRO’s High Resolution Imaging Science Experiment (HiRISE) camera, operated by the University of Arizona,
show that solid carbon dioxide is found on these slopes in the winter, and that the gullies form in early spring.
Experiments on Earth show that sublimation during the descent provides chunks of dry ice with a lubricating
layer, so that they slip on low-angle slopes, and they push sand into levees. Further evidence for the roles of
CO2 ice comes from HiRISE images that show blocks sitting in the grooves, and later sublimating. This research
is published in Icarus by Serina Diniega, a planetary scientist at NASA’s Jet Propulsion Laboratory, and Alfred
McEwen, a professor of planetary science at the University of Arizona. (NASA/JPL-Caltech/Univ. of Arizona)
http://1.usa.gov/1b4OtVu
Voyager is close
to the edge
The veteran Voyager spacecraft are
continuing their departure from the
solar system and gathering more data
on the behaviour of charged particles
at the outer reaches of the Sun’s magnetic field.
Voyager 1 is now in a region called
the magnetic highway (or depletion region), and has documented
a relatively sudden drop in charged
particles originating from the Sun
and moving outwards along the
magnetic field lines, while those
moving perpendicular to the field
did not decrease as quickly. Cosmic
rays from outside the heliosphere
increased, another sign that the
spacecraft is approaching the edge
of the heliopause. The third indicator that Voyager is leaving the heliopause would be an abrupt change in
the direction of the magnetic field
lines, as interstellar fields take over
from the Sun’s field; this has not
been detected, so Voyager 1 is considered to be still within our solar
system.
The spacecraft is close enough to
the edge of the Sun’s influence to be
able to detect low-energy cosmic rays
from nearby dying stars, but galactic
cosmic-ray levels varied considerably
in the eight months of data, another
sign that the Sun’s field is still controlling Voyager’s environment.
Three papers published in Science
in June focus on data from Voyager 1
between May and September 2012
using the cosmic-ray, low-energy
charged particle and magnetometer
instruments, with some additional
charged-particle data continuing
until April this year. The data on the
outer reaches of the heliosphere have
features in common with the readings made when Voyager left Jupiter’s
magnetosphere, 34 years ago. Voyager 2, launched later, is still within
the heliosphere.
http://www.nasa.gov/voyager
http://voyager.jpl.nasa.gov
Herschel runs
out of helium
The European Space Agency’s Herschel space observatory finished its
mission on 29 April this year, almost
four years after its launch, when its
helium coolant ran out. All operations were terminated on 17 June,
after a period during which the
spacecraft, still in contact with mission control, served as a testbed for
control techniques that cannot normally be tested in flight.
“Normally, our top goal is to maximize scientific return, and we never
do anything that might interrupt
observations or put the satellite at
risk,” saidMicha Schmidt, Herschel’s
Spacecraft Operations Manager at
ESA’s European Space Operations
Centre (ESOC). “But the end of science meant we had a sophisticated
spacecraft at our disposal on which
we could conduct technical testing
and validate techniques, software
and the functionality of systems
that are going to be reused on future
spacecraft. This was a major bonus.”
Requests for in-orbit validation
and analysis of hardware and software came from the mission-control
teams at ESOC, from the European
industry teams that built the satellite
and its components, and from science
instrument teams. Engineers worked
with Herschel’s Visual Monitoring
Camera for the ExoMars team who
will be using a similar model on their
mission, for example, and carried out
some reaction-wheel tests for the
Euclid team.
A&G • August 2013 • Vol. 54
News • Mission Update
Curiosity gives the big picture
The NASA team behind the Curiosity rover and the Mars Science Laboratory have stitched together a billion-pixel view of Mars from the rover’s data so
far. Observers on-line can pan and zoom though a 360° panorama around Rocknest – the place where the rover started to analyse samples of soil and
rock, within Gale Crater. The image uses 850 frames from the telephoto camera of Curiosity’s Mast Camera instrument, supplemented with 21 frames
from the Mastcam’s wider-angle camera and 25 black-and-white frames – mostly of the rover itself – from the Navigation Camera. The images were
taken on several different Mars days between 5 October and 16 November 2012.
http://mars.nasa.gov/bp1
Herschel carried out its scientific
operations at the L2 Sun–Earth
Lagrange point; many of the final
manoeuvres for the spacecraft were
designed to boost it into a helio­
centric orbit both further out and
slower than that of Earth. At one
stage Herschel fired its thrusters for 7
hours and 45 minutes, using up most
of the remaining fuel.
http://sci.esa.int/herschel
Gaia ready to go
ESA’s precision-astrometry mission
has come a step closer to launch with
the completion of work in Europe on
the Gaia satellite before its dispatch
for Kourou in French Guiana, where
it will be launched later this year.
“Gaia builds on the technical
and scientific heritage of ESA’s
star-mapping Hipparcos mission,
reflecting the continued expertise of
the space industry and the scientific
community across Europe,” said
Alvaro Giménez, ESA’s Director of
Science and Robotic Exploration.
“It’s extremely rewarding to see the
next generation of our high-precision observatories built and ready to
answer fundamental questions about
the cosmos.”
A&G • August 2013 • Vol. 54 During its five-year mission, the
spacecraft will spin slowly, sweeping its two telescopes equipped with
the largest digital camera ever flown
in space – with nearly a billion pixels – across the entire sky. The goal
is to produce a 3D map of the Milky
Way, repeatedly observing a billion
stars, some 1% of the stars in the galaxy. Throughout the five years of the
mission, Gaia will measure each star
70 times, making roughly 40 million
observations per day!
Such precise data on the positions
of stars allows researchers to map
the galaxy, trace the distribution of
dark matter and test Einstein’s General Theory of Relativity. Gaia will
also be able to detect new asteroids
in the solar system, and new planets
in other star systems.
http://bit.ly/11ZJvX0
Saturn’s Great
White Spots
Every 30 years or so a planet-wide
storm erupts on Saturn, causing
optical effects known as a Great
White Spot. Thirty Earth years are
one year on Saturn, of course. The
spot appears to arise from sustained
convection, according to models
published in Nature Geoscience,
based on high-resolution images
from Cassini.
Great White Spots have been
observed six times since 1876; the
most recent example was first seen
in 2010 and dissipated in 2011. It
became an enormous disturbance,
extending over 10 000 km at cloud
level, with its effects spreading right
round the planet and convection visible on timescales of hours, indicating extreme conditions.
A team of researchers led by E
García-Melendo of the Fundació
Observatori Esteve Duran, Seva,
Spain, used Cassini’s Imaging Science Subsystem to observe the
feature repeatedly and use cloud
positions to map wind vectors.
They found peak wind velocities of
160 ± 30 m s –1. Modelling the wind
patterns suggested that sustained
convection could trigger the storms,
within a background of sheared flow
at different atmospheric depths; mass
upwelling, stopping just below the
troposphere, could have the same
effect. The model also indicated that
the convective activity needs to take
place between 31.5°N and 32.4°N in
order to trigger the storms; this is the
same as the latitudes where massive
clusters of clouds that appear like
cumulus clouds are found.
http://bit.ly/19WqD0a
Zoë goes back
to the desert
An autonomous solar-powered rover
named Zoë is heading back to the
Atacama desert, and this time it has
a drill with a 1 m reach.
The rover is on a NASA astrobiology mission, led by Carnegie Mellon
University and the SETI Institute. In
2005 this rover mapped microbial
life in the Atacama desert, and now
it is testing possibilities for a Mars
rover to follow NASA’s current Mars
rover, Curiosity. Direct evidence of
life is considered more likely in the
subsurface, protected from extremes
of climate and radiation, so the goal
for Zoë is to see what evidence this
1 m auger can extract from the soils
of the Atacama desert. The rover
data will be compared with a field
study carried out in 2012 by the
research team using neutron detection and spectrometry on handdrilled boreholes.
http://bit.ly/18uX04W
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