- 4425
- MARS -
craters filled with water? - New research shows that the Gale Crater,
the landing spot for NASA’s “MSL Curiosity”, held water for a longer time than
scientists thought. Life needs water,
and it needs stability. So, if Gale Crater held water for a long time, it
strengthens the idea that Mars could’ve supported life.
------------------------- 4425 - MARS - craters filled with water?
- Mars’ Gale Crater was filled with water for
much longer than anyone thought. We
know that Mars was once warm and wet, a conclusion that was less certain a
couple of decades ago.
-
- The Gale Crater is an ancient paleolake,
and research suggests that the region could’ve been exposed to water for a
longer duration than thought. But was it liquid water? The research is titled “Ice? Salt? Pressure?
-
- Sediment deformation structures are
evidence of late-stage shallow groundwater in Gale crater. We know that water played a role in shaping
the Martian surface. Multiple rovers and orbiters have given us ample evidence
of that. Orbital images show clear examples of ancient deltas. We also have
many images of sedimentary rock, with its tell-tale layered structure, laid
down in the presence of water.
-
- The Gale Crater and the landforms within
it, Mount Sharp, is the dominant feature in the crater and
rises 18,000 feet. It’s made up of sedimentary layers that have been eroded
over time. But it has substructures that show its detailed history.
-
- Wind-deposited layers were contorted into
strange shapes, which suggests the sand had been deformed shortly after being
laid down. These structures point to the presence of water just below the
surface.
-
- cientisSts found something odd in the
overlying windborne sandstone: deformed layers that could only have been formed
in the presence of water. The sandstone revealed that water was probably
abundant more recently, and for longer, than previously thought.
-
- This water might have been pressurized
liquid, forced into and deforming the sediment; frozen, with the repeat
freezing and thawing process causing the deformation; or briny, and subject to
large temperature swings.
-
- By the middle of Mars’ “Hesperian Period”,
the planet lost its water. The Hesperian’s boundaries in time are uncertain,
but it’s generally thought of as the transition from the heavy bombardment
period to the dry Mars we know today. The Hesperian could’ve ended between 3.2
and 2.0 billion years ago. The “Noachian” preceded it, and the “Amazonian”
followed it.
-
- This suggests that Mars had abundant
subsurface water toward the end of the Hesperian. The evidence is in MSL
Curiosity’s images of different sedimentary rocks on Gale Crater’s Mt. Sharp. When sediments are moved by flowing water in
rivers, or by the wind blowing, they leave characteristic structures which can
act like fingerprints of the ancient processes that formed them.
-
- “MSL Curiosity” slowly worked its way up Mt.
Sharp, studying the rocks at different elevations as it ascended. As expected,
it found younger rocks the higher it went. Eventually, it reached the Stimson
formation. The “Stimson formation” is the remnant of an ancient windborne
desert dune field.
-
- Usually, the wind deposits sediment in a
very regular, predictable way.
Surprisingly, they found that these wind-deposited layers were contorted
into strange shapes, which suggests the sand had been deformed shortly after
being laid down. These structures point to the presence of water just below the
surface.
-
- In the “Brackenberry outcrop feature”, the
sedimentary rocks show evidence of deformation by water. There are laminations
in various states of deformity, becoming more pronounced in the feature
geologists call the cusp core. In the “cusp core”, wind-ripple laminations bend
toward the vertical and become incoherent.
-
- There are three mechanisms that can explain
the deformed features, and they all involve water. They’re also not mutually
exclusive. High-pressure water could’ve
overcome the strength of the rock and deformed it. Large ice deposits on top of
the structure could’ve caused deformation, as could freeze/thaw cycles of water
inside the rock. The third explanation involves sediment rock weakly bound
together by evaporites. Thermal expansion and contraction of the evaporites can
deform the rock.
-
- The layers of sediment in the crater reveal
a shift from a wet environment to a drier one over time reflecting Mars’
transition from humid and habitable environment to inhospitable desert world. But these water-formed structures in the
desert sandstone show that water persisted on Mars much later than previously
thought.
-
- These finding extends the timeline of water
persisting in the region surrounding Gale crater, and so the whole region could
have been habitable for longer than previously thought. Mars is an instructive example. If it
remained habitable for longer than we thought, it was likely only marginally
inhabitable.
-
- There are a bewildering number of variables
that go into making Earth the living oasis that it is. We’re much more likely
to stumble on other planets like Mars, which were once habitable and maybe even
harbored simple life. If Earth’s long-lived habitability is the outlier, and
Mars’ marginal, interrupted habitability is more likely, we can expect to find
many planets like it that were once alive but are now long dead.
-
- How lucky we are to be alive!
-
-
April 9, 2023 MARS
- craters filled with water? 4425
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------
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------ “Jim Detrick” -----------
--------------------- --- Wednesday, April 10,
2024
---------------------------------
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