- 4531 -
MARS - possible life? On Earth, these types of features in rocks
are often associated with the fossilized record of microbes living in the
subsurface. NASA's Perseverance rover
has discovered a rock on Mars that may have once hosted microbial life.
--------------------------- 4531 - MARS - possible life?
- The rock, nicknamed “Cheyava Falls”, has
chemical compositions and structures that could have been formed by ancient
life, although non-biological processes cannot yet be ruled out.
-
- The “rover” came across this intriguing,
arrowhead-shaped rock that hosts chemical signatures and structures that could
have been formed by microbial life billions of years ago, when Mars was
significantly wetter than it is today. Inside the rock, which scientists have
nicknamed "Cheyava Falls,"
-
- Perseverance's instruments detected organic
compounds, which are precursors to the chemistry of life as we know it. Wisping
through the length of the rock are veins of calcium sulfate, which are mineral
deposits that suggest water, also essential for life, once ran through the
rock.
-
- The rover also found dozens of
millimeter-sized splotches, each surrounded by a black ring and mimicking the
appearance of leopard spots. These rings contain iron and phosphate, which are
also seen on Earth as a result of microbe-led chemical reactions.
-
- These spots are a big surprise. On Earth, these types of features in rocks
are often associated with the fossilized record of microbes living in the
subsurface. We've never seen these three
things together on Mars before.
-
- “Cheyava Falls” sits at the edge of an
ancient, 400-meter-wide river valley named “Neretva Vallis”. Scientists suspect
this ancient channel was carved out long ago due to water gushing into Jezero
Crater; Neretva Vallis runs along the inner wall of this region.
-
- In one possible scenario, mud that already
possessed organic compounds got dumped into the valley and later cemented into
the Cheyava Falls rock, which Perseverance sampled. A second episode of water
oozing into the formed rock would have created the object's calcium sulfate
veins and black-ringed spots the team sees today.
-
- The rock's visible features aren’t
irrefutable evidence of ancient microbial life on Mars, not yet, at least. It
is possible, for instance, that the observed calcium sulfate entered the rock
at uninhabitably high temperatures, perhaps during a nearby volcanic event.
However, whether such non-biological chemical reactions could have resulted in
the observed black-ringed spots is an open question.
-
- We have zapped that rock with lasers and
X-rays and imaged it literally day and night from just about every angle
imaginable. To fully grasp what really
unfolded in the ancient river valley billions of years ago, scientists are keen
to get the Cheyava Falls sample to Earth, where it can be scrutinized with
powerful instruments that Perseverance’s limited suite doesn't have.
-
- The search for habitability elsewhere in
the universe can be reduced to the search for water. We haven't yet found
lifeforms that detach this substance from our conception of "life"
itself, so we have no choice but to accept the cosmic water trail as our north
star in the quest to find worlds that mirror our own.
-
- It is for this reason that scientists jump
for joy a little when they find an exoplanet likely to hold any water at all,
but particularly liquid water, rather than ice or water vapor. A tantalizing
planet outside the solar system may have a temperate water ocean about half the
size of the Atlantic.
-
- Of all currently known temperate
exoplanets, “LHS 1140 b” could well be our best bet to one day indirectly
confirm liquid water on the surface of an alien world beyond our solar system.
-
- “LHS 1140 b” exoplanet orbits a red dwarf
star about a fifth the size of the sun and sits 48 light-years away from Earth
in the constellation Cetus which, as luck would have it, translates to
"the whale." But most important about LHS 1140 b is the fact that it
lives in its star's habitable zone, otherwise known as its "Goldilocks
zone." As that nickname would suggest, this is the area around a star
where it's neither too hot nor too cold for a world to host liquid water, but
rather fits the standard by which the fairy tale character Goldilocks lives.
-
- This is the first time we have ever seen a
hint of an atmosphere on a habitable zone rocky or ice-rich exoplanet. Though it has been making headlines now due
to the new study involving JWST data, LHS 1140 b has actually been on planetary
hunters' radars for some time. In fact, experts had already theorized that this
could be a water world in the past, and even shared similar sentiments about
how it could offer humanity the first-ever direct evidence of exoplanetary
liquid water.
-
- However, there was something missing until
now: the James Webb Space Telescope's keen eye. It was necessary because, for a long time,
there was something like a gap in the literature about LHS 1140 b.
-
- Basically, the trouble was that scientists
couldn't quite confirm whether the exoplanet is a mini-Neptune, a planet less
massive than our original Neptune, but one that still has Neptunian
characteristics, or a super Earth. A super Earth is a world that's larger than
Earth, but still either rocky or water-rich. The latter typically sounds the
"potential habitability" alarm, and the JWST, scientists had
imagined, could be the one to set it off.
-
- This only "strongly excluded" the
mini-Neptune scenario, but also confirmed the world may have a nitrogen-laced
atmosphere like Earth does. While it is
still only a tentative result, the presence of a nitrogen-rich atmosphere would
suggest the planet has retained a substantial atmosphere, creating conditions
that might support liquid water.
-
- The TRAPPIST-1 system is a planetary
lineup that looks almost disturbingly similar to our solar system's structure.
The septet of orbs resembles our octet and some of them are in the habitable
zone like Earth is.
-
- JWST study actually complicated the search
for habitability in TRAPPIST-1 quite recently. It revealed that the system's
anchor star is incredibly active in such a way that it could skew our
observations, making us believe a world in the system is habitable when it
really isn't. Even the JWST has its limitations.
-
- The star LHS 1140 appears to be calmer and
less active making it significantly less challenging to disentangle LHS 1140
b's atmosphere from stellar signals caused by starspots.
The JWST data further suggests
the exoplanet's mass might be made of between 10 percent and 20 percent liquid
water.
-
- It could look like a snowball, essentially,
that orbits its star while rotating in such a way that one side always faces
that star. It's kind of like the moon's orbit around Earth; we can't ever see
the far side of the moon because the moon rotates at the same rate it revolves
around Earth. One side never faces us, and the other always does.
-
- Similarly, this would mean that, if the
JWST's illustration of the LHS 1140 b scene is correct, the side of the planet
always facing its sun would be exposed to lots of heat. This would be the part
of the snowball that's "melted" into a liquid ocean.
-
- Current models indicate that if LHS 1140 b
has an Earth-like atmosphere, it would be a snowball planet with a bull's-eye
ocean about 2,485 miles in diameter. The surface temperature of the ocean may
very well even be a
"comfortable" 68 degrees Fahrenheit.
-
-
July 26, 2024 MARS -
possible life? 4531
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--------------------- --- Monday, July 29, 2024
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