- PASADENA -- Signs of past
water on the surface of Mars just keep getting clearer, with new discoveries
from both NASA rovers.
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- Spirit has discovered hematite, an iron mineral that
is usually formed in water. It is abundant at Opportunity's site, but not
seen before on the other side of the planet. Opportunity, meanwhile, has
extended its evidence of water further back in time, through possible past
cycles of wet and dry climate.
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- The rover's missions have both entered new phases. Opportunity
has descended more than five metres into Endurance crater, while Spirit
has begun its reconnaissance at the base of Columbia hills. The prospects
are so exciting, says lead scientist Steve Squyres, that "it felt
to us in the last couple of weeks like the [five-month-long] mission has
started all over again".
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- Spirit's discovery of the first hematite seen at Gusev
crater came from a peculiar rock dubbed "pot of gold". The fist-sized
rock has strange round nodules that stick out on the end of stalks and
also has very distinct planar layering. Ý The nodular nuggets of
the "pot of gold" rock. The observed area is 3cm tall (Image:
NASA/JPL/Cornell/USGS)
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- Despite detailed inspection with the microscopic imager,
"we have not got this thing figured out yet," Squyres admitted
at a press conference at NASA's Jet Propulsion Laboratory, in Pasadena,
California on Friday. "I don't know how these things formed, and it's
driving me nuts!"
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- What is clear, Squyres said, is that Spirit is now in
a very different geological zone and so has a good chance of learning about
very different episodes in Martian history.
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- Hazardous drive
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- Opportunity's hazardous drive down into Endurance crater
has taken it to lower rock strata and hence back in geological time. And
the team's risk taking has already paid off with further evidence that
water existed on the surface in the past. That shows water was present
not just at one point in time, but over an extended period.
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- Opportunity landed in the much smaller Eagle crater,
and found a whole suite of evidence for liquid water. But the stadium-sized
Endurance crater is much deeper.
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- In Endurance, the rover found a layer that matched the
one at Eagle, and then delved down beyond it, past a geological "contact"
with a separate, older layer of rock. And conditions during the deposition
of that rock seem to be essentially the same, indicating that water either
persisted on the surface for a long time, or else returned during repeated
wet spells.
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- The layers close by and some within immediate reach of
Opportunity's instrument arm have been divided by the team into geological
units A through to E. So far, only A and B have been examined, so the coming
days will quickly extend the record further back in time.
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