- 4485
- MARS ROCK
SAMPLES? - “Perseverance” rover's Mars rock sample may
contain best evidence of possible ancient life.
This rock material has been stored in the rover's sample tubes. Tubes were dropped on the surface of Mars
and contained within the rover itself while wheeling about within Jezero
Crater.
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------------------------------------------ 4485 - MARS ROCK SAMPLES?
- Given the samples of Mars that Perseverance
has collected so far, could one of those specimens be evidence of past
microbial life on the Red Planet? The
preliminary finding heightens the need for returning these Mars samples to
Earth, so that these prized collectibles from the Red Planet can be sent to
laboratories for rigorous analysis.
-
- "Lefroy Bay," sample was found to have hydrated
silica. The sample may have been
deposited either in a lake or in a groundwater system. Both are very important
settings for understanding Mars habitability and habitation at Jezero
Crater.
-
- The 'Margin Unit' samples are onboard
Perseverance. These samples have
abundant carbonate and silica, clearly indicating a dominant role for liquid
water in their formation.
-
- But whether that water was surface water in
a lake or river, or groundwater, remains uncertain. Either could constitute an ancient, greater
than 3.4 billion years old, habitable Martian environment.
-
- These samples host phases that on Earth are
very useful for establishing "paleo-envieonmental" conditions. They can preserve biosignatures. As such these samples are uniquely important
for return to Earth for further study.
-
- Perseverance is "just about to make a
really fundamental transition in the exploration of the environment that we
have been working in. This will not be a
great terrain for driving a rover across.
-
- So far, the Mars machinery has traversed
some 17 miles after it was lowered to the area by skycrane on February 18,
2021. The robot's objective is set in stone:
Seek signs of ancient life and collect samples of rock and regolith for
possible Earth return.
-
- Scientists believe this area was once
flooded with water and was home to an ancient river delta. The anticipation is
that Jezero Crater is quite literally, "spilling" the beans about its
on-again, off-again nature of the wet past of Mars. More than 3.5 billion years
ago, river channels spilled over the crater wall and created a lake.
-
- What's possible is that microbial life
could have lived in Jezero during one or more of those wet periods. If true,
evidence of leftovers from those little critters might be discovered in lakebed
or shoreline sediments.
-
- The Perseverance rover has the lost the
wind sensors that are part of the Mars Environmental Dynamics Analyzer
(MEDA). Also, the spectroscopy parts of
the robotic arm-mounted Scanning Habitable Environments with Raman &
Luminescence for Organics & Chemicals, SHERLOC for short, are challenged.
That's due to a lens cover no longer working properly.
-
- The rover was dispatched to Mars with 38
tubes that could be used for rock, regolith, and even atmospheric
sampling. The on-duty robot has sampled
igneous rocks, mudstone, sandstone/pebble conglomerate,
carbonate-silica-olivine, as well as top side Mars sand and snagged a whiff of
Martian atmosphere.
-
- Earlier in its trekking of Mars,
Perseverance dropped 10 sealed sample tubes at a depot location dubbed
"Three Forks" in Jezero Crater. The intent is that a Mars Sample
Return (MSR) mission in the future would pick up sample tubes for rocketing
those bits and pieces of Mars back to Earth.
-
- In the rover's travel itinerary is
completing tasks at an area called “Bright Angel”, then move up onto the crater
rim, where the rover can survey fundamentally different geology. In ascending the rim they will expeditiously
complete the sampling.
-
- The “pit crater” possibly opens into a
larger cave that could provide a sheltered environment for both astronauts and
hypothetical Martian life. This pit
crater on Arsia Mons was imaged by the High Resolution Imaging Science
Experiment (HiRISE) instrument on the Mars Reconnaissance Orbiter.
-
- The pit is on the flank of an ancient volcano
on Mars has generated excitement recently because of what it could reveal
beneath the surface of the Red Planet. Here's what that means.
-
- The pit, which is only a few meters across,
was actually imaged on August 15, 2022, by NASA's Mars Reconnaissance Orbiter,
which was about 159 miles above the Martian surface at the time. This hole in
the ground is also not alone. It's one of many seen on the flanks of a trio of
large volcanoes in the Tharsis region of Mars.
-
- This particular pit is found on a lava flow
on the extinct volcano Arsia Mons, and appears to be a vertical shaft. Is it just a narrow pit, or does it lead to
a much larger and remarkable cavern? Or, could it perhaps be a really deep lava
tube formed underground long ago when the volcano was still active?
-
- There are several reasons why pits and caves
on Mars are of interest. For one, they could provide shelter for astronauts in
the future; because Mars has a thin atmosphere and lacks a global magnetic
field, it cannot ward off radiation from space the way that Earth does.
Consequently, radiation exposure on the Martian surface averages between 40 and
50 times greater than on Earth.
-
- The other aspect of these pits is they might
not just provide shelter for human astronauts; they could hold astrobiological
interest in the sense that they could have been sheltered abodes for Martian
life in the past, perhaps even today, if microbial life indeed exists there.
-
- The presence of these so-called holes on the
flanks of volcanoes is a big clue that they are probably connected to volcanic
activity on Mars. Channels of lava can flow away from a volcano underground;
when the volcano grows extinct, the channel empties. That leaves behind a long,
underground tube. We see such tubes not only on Mars, but also on the moon and
on Earth.
-
- Sometimes, if the crust is thin enough, the
ceiling of these tubes collapses. If a collapse happens along the tube's entire
length, it forms a feature called a “rille”, which is a long trench commonly
found on the moon and sometimes in other areas of Mars.
-
- If the tube's ceiling just collapses in
small areas, however, we get pits like those imaged on Arsia Mons. Planetary
scientists have also seen pit chains on the flanks of Martian volcanoes, which
are linear stretches of multiple pits seemingly following the length of a lava
tube.
-
- How deep these pits descend is a mystery,
however, and it remains uncertain whether the pits open into a large cavern or
whether they are contained to a small, cylindrical depression. Some Martian
pits have been imaged when the sun is high enough in the sky to illuminate what
appears to be the sides of the pit wall, which implies they are shafts that go
straight down into the flank of the volcano.
-
- This would seem to suggest these pits are
unlikely to open into larger caves or tubes. If so, this would make them
similar to pit craters found on the volcanic mountains of Hawaii, which also
don't open up to anything larger and which are produced by the collapse of
material deeper underground, which causes material above to sink. However, pits on the moon have been shown to
have boulder-strewn floors that appear as though they could lead to a larger
subterranean volume.
-
- Pits can also be formed through tectonic
stresses that fracture a world's surface, and these may be less likely to lead
to a larger cavern. And finally, one other, possibly less likely, explanation
is that these pits open up into where underground rivers once flowed billions
of years ago.
-
- We can see a similar phenomenon on Earth,
in the form of a geological feature called a 'karst”, which forms when
limestone bedrock dissolves and weakens, creating pits and sinkholes that open
up into areas of groundwater.
-
- If that is the case on Mars, then, if the
Red Planet ever once had life, those organisms may have sheltered in karsts.
Indeed, running water down the flank of an active volcano would have been warm,
providing the perfect protected environment for life to flourish and stay safe.
-
- We'll only have some concrete answers after
future missions actually explore some of these pits. Though a rover that drives
to the edge of a pit would be unable to descend, an airborne mission along the
same lines as NASA's “Ingenuity helicopter”, which operated on Mars for three
years before it became grounded in January 2024 after damaging one of its rotor
blades, would have the ability to hover over and descend into a pit to see what
is down there.
-
- If these pits do open up into caves, they
may become a preferred landing site for future crewed missions to Mars that
will require astronauts to build a sheltered basecamp away from the world's
unrelenting radiation.
-
-
June 8, 2024 MARS
ROCK SAMPLES? 4495
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------ “Jim Detrick” -----------
--------------------- --- Sunday, June 9, 2024
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