[meteorite-list] Phobos Could Be A Key Test for Mars Sample Return

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Fri, 9 Feb 2007 12:41:16 -0800 (PST)
Message-ID: <200702092041.MAA16935_at_zagami.jpl.nasa.gov>

http://news.bbc.co.uk/2/hi/science/nature/6324923.stm

Martian moon 'could be key test'
By Jonathan Amos
BBC News
February 9, 2007

Mars' moon Phobos could be the target for a technology trial that would
seek to return rock samples to Earth.

A UK team is developing a concept mission that aims to land a spacecraft
on the potato-shaped object and grab material off its surface.

These small rock fragments would then be despatched to Earth in a capsule.

"It is being seen as a technological demonstrator for an eventual Mars
sample return," said Dr Andrew Ball from the Open University.

Those aspects of the mission that worked well could be incorporated into
a full-scale assault on the Red Planet.

Both Europe and the US have made the objective of bringing back Martian
rocks to Earth laboratories a top priority for their space programmes. A
joint venture is likely to occur within the next 15-20 years.

But getting on and off a large planet will be extremely difficult, and
the British satellite manufacturer Astrium is proposing to test the
required technologies on the low-gravity target of Phobos first.

"It would be a three-year mission. We're looking at a 2016 launch," said
Marie-Claire Perkinson, a principal mission systems engineer at the
Stevenage company.

Many links

Even so, the Phobos concept has a number of challenging steps, all of
them capable of killing the mission if a single element goes wrong.

It is envisaged that a "mothership", powered by an ion engine, would fly
into orbit around Mars where it would release a lander craft down on to
the surface of the moon.

It's challenging because it requires a lot of new technology development
Marie-Claire Perkinson, Astrium

This robot vehicle might do some in-situ experiments but its main task
would be to core, drill, or scoop up surface "soil" into a sealed vessel.

Then, it would lift off from Phobos using chemical thrusters to attempt
to dock with, or be captured by, the passing mothership. If that
succeeds, the sample vessel would be transferred across and packaged
inside an additional bio-secure sealed-container ready for the trip home.

Close to Earth, this capsule would be jettisoned into the atmosphere to
make a hard landing; it would need no parachute assistance.

"It's really the sample transfer chain which is the critical issue -
right from landing on Phobos and taking the sample, and then passing it
through the various vehicles to return to Earth," explained Ms Perkinson.

"It's challenging because it requires a lot of new technology
development, and it's reliant on a lot of mechanisms, which is something
we usually try to avoid."

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HOW THE PHOBOS SAMPLE RETURN MISSION MIGHT LOOK
Mission architecture (BBC)

(1) The spacecraft could leave in 2016 when Earth and Mars are in a
favourable alignment, reducing the mission length to three years
(2) Cruise phase would use a solar-electric engine. This relies on solar
power to accelerate xenon ions to produce forward thrust
(3) The mothership would go into orbit around Mars; the lander would be
ejected to make its own way down to the surface of Phobos
(4) The lander could do some in-situ experiments, but its primary
objective would be to package away surface material
(5) After lift-off, the lander would dock with, or be captured by, the
mothership - a key test for Mars sample return technology
(6) The Phobos samples will be transferred to a sealed and bio-secure
re-entry capsule for the journey home:
(7) After ejection and Earth re-entry, the capsule would crash-land; no
parachute would be used to slow its fall
----------------------------------------------------------------------

The concept is being considered by the European Space Agency (Esa) under
its Aurora programme for Solar System exploration.

Already approved and in development is a robot rover that will trundle
across the surface of the Red Planet to look for signs of past or
present life; and Astrium is working on the vehicle's chassis.

A precursor Mars-sample-return mission could get the go-ahead from Esa
in the next couple of years. French industry is interested in leading
this project and is preparing its own, competing concept.

Whoever is chosen may well have to watch the Russians give it a go
first. They are currently working on a project known as Phobos-Grunt,
which could fly as early as 2009.

But leading out of the box is not a guarantee of success. Getting down
on to a small low-gravity body has its own difficulties. The wrong
approach could crush landing legs or even result in the vehicle bouncing
straight back off into space.

Such problems were amply demonstrated by the recent Japanese attempts to
grab samples off the surface of an asteroid.

It is still not clear whether the Hayabusa spacecraft managed to capture
any material and the probe's return to Earth is still haunted by
uncertainty.

Moon 'death'

For Dr Ball, a consultant on the Astrium proposal, Phobos represents a
fascinating subject for study in its own right, over and above any
eventual objective of getting down to the surface of the Red Planet.

The moon, like its sister Deimos, is asteroid-like in appearance - in
fact, these two satellites are very probably "primitive" asteroids that
were captured into Mars' orbit by its gravity.

----------------------------------------------------------------------

PHOBOS - MARTIAN MOON
Phobos (Nasa)
Measures 27 x 22 x 18km; could be a captured asteroid
Orbits less than 6,000km above Mars; slowly falling inwards
First high-res probe images taken by Mariner 7 in 1971
Dedicated Soviet probes, Phobos 1 & 2, were lost
10km-wide Stickney crater (above) records huge impact

----------------------------------------------------------------------

As such, their construction and composition may have much to say about
the formation and early evolution of the Solar System.

Close study should also refine estimates for the expected "death" of
Phobos. Its orbit around Mars is shrinking and in a few tens of millions
of years it will either fall on to the planet or, more likely, shatter
under tidal forces into countless pieces and form a ring.

One of the moon's most notable features is the system of grooves that
cross its surface. These are assumed to be the result of collisions with
rocks blasted off the surface of Mars by space impacts.

This raises the intriguing prospect that Phobos may actually be littered
with Martian material.

"So, with this mission, you could get two for one," said Dr Ball.

"When there's a large impact on Mars, ejecta gets thrown up, and some of
that can hit Phobos. Over billions of years, Phobos should have
accumulated some fraction of Martian soil in its surface.

"In doing this mission, we'd not only be demonstrating many of the
technologies required for a Mars sample return, but we may even get some
Martian material itself."

The size of the Phobos sample would not need to be very large.

Some 200g would be enough to keep current astro-labs busy and have a
portion in reserve for future analysis using yet-to-be developed
techniques - a standard approach when dealing with scarce
extra-terrestrial material.
Received on Fri 09 Feb 2007 03:41:16 PM PST