the explorers journal - The Explorers Club

elentless eruptions of magma and steam. We
have found aqueous silicates around what may
have been hot springs of volcanic fumaroles. At
a place we call “Home Plate,” a circular feature in
the Inner Basin of the Columbia Hills, Spirit found
a collection of layered pyroclastic deposits (coarse
grains lying beneath much finer material) which
fits the pattern of accumulation of material raining
down during a volcanic eruption. In contrast to the
steamy and violent environment encountered by
Spirit, Opportunity, working halfway around the
planet, has found evidence of a wetter environment
where acidic water once saturated the ground and
occasionally flowed across its surface.
EJ: So where are the rovers now
SS: In April 2009—some 800 Sols, or Martian days,
into the project and with more than 7.5 kilometers
traveled—Spirit became trapped in deep, soft sand
on the west side of Home Plate, eventually losing
use of its right front wheel and right rear wheel in
an attempt to free itself. After multiple attempts to
dislodge the rover, we have decided for now to
focus on experiments that will tell us information
about its current location. As it turns out the “sand
trap,” which we have nicknamed “Troy,” happens
to be an excellent site for research purposes.
Already, this has begun to yield interesting results.
Just below the surface, the rover has found
sulfate-rich deposits beneath its left wheels, which
we believe were formed in steam vents associated
with water-charged explosive volcanism. Spirit
is sitting on the edge of a small crater, astride a
boundary between crusty sulfate-rich deposits
and soils with an average concentration of sulfur.
We are also hoping that, from its stationary position,
we can use radio tracking of Spirit to monitor
any wobble in the planet’s axis of rotation, which
could tell us whether Mars’ core is molten or solid.
The biggest problem we face with Spirit now is
that winter is setting in the southern hemisphere
and the rover’s solar array is tilted 9 degrees to
the south, away from the Sun, rather than to the
north—as it would be if the rover were mobile—limiting
its solar power supply. Spirit will go semi-dormant
for the remainder of the Martian winter until
the rover begins receiving enough solar power to
recharge and resume operations.
Opportunity, on the other hand, has just
wrapped up operations at the Victoria Crater
some 19 kilometers from its landing site and is
now en route to Endeavour Crater, 11 kilometers
away. The craters, by the way, are named in honor
of great ships of discovery. During the traverse,
the rover has encountered several interesting features
on the otherwise barren plain. One, which
we dubbed Marquette Island, is a strange basaltic
rock about the size of a basketball that appears
to have come from deep in the Martian crust. We
think it is ejecta from a distant crater. The rover
also found two iron-rich meteorites of a type we
find on Earth, which we named Block Island and
Shelter Island. En route, we are having the rover
investigate Concepción Crater, a small, young
crater from a more recent impact.
Opportunity’s probe of the craters within the
Meridiani Planum has revealed that surface waters
evaporated there, leaving behind sulfate-rich
sands that, over time, have been shaped by wind
and solidified by groundwater.
EJ: Tell us about the Mars Reconnaissance
Orbiter (MRO), which recently spied depressions—thought
to be lakes—with drainage patterns
consistent with flowing water near the Ares Vallis,
a great gorge that runs along the Martian equator.
SS: From the information we have from the rovers,
it seems clear that water of some sort once flowed
across the Martian landscape. The new images
seem to confirm that. The relationship is synergistic
between the rovers and the MRO, which
provides a global view of the planet versus the
detailed inspection we gain on the ground. Each
informs the movements and operations of the others.
The MRO is a key component of rover planning
activity. MRO will see something that may
be worth a rover look. Also, MRO’s companion
orbiter Odyssey provides an important communications
relay between Earth-based operations
and the rovers at times when their locations are
on the far side of the planet from Earth.
EJ: What are your future plans for the project
SS: In addition to continuing to use the rovers as
long as they remain in service, we are also working
on the Mars Science Laboratory, which is somewhat
more robust than Spirit and Opportunity.
More than twice as large as the current rovers,
it will collect Martian soil and rock samples and
analyze them for organic compounds that might
attest life of some sort. For more on the state of
affairs on Mars, visit: mars.nasa.gov
the explorers journal