One of the greatest mysteries of the solar system is whether Mars has, or once had microbial
life.
We know it was once like earth.
And it seems to hint that it could be an abode of life.
So here are ten indicators that Mars may have had, and may still have life.
10.
The Viking Experiments
In 1976, NASA successfully landed the Viking one and two missions on the surface of Mars.
One of the experiments onboard the landers was the Labeled Release experiment designed
to detect Martian microbial life.
Essentially, the experiment exposed nutrients to the Martian environment and then looked
for any evidence that something was metabolizing it.
The experiment returned a positive.
This detection has been problematic and controversial ever since.
Part of the problem is that other experiments on the lander failed to detect organics.
Another part is that the Martian surface is an extremely inhospitable environment.
Problem one is radiation from the sun, and problem two are the presence of chemicals
such as perchlorate, which can destroy organic compounds.
This reaction would produce chloromethane and dichloromethane as by products, and those
were apparently detected opening up the possibility that the detection was real, and the reason
that organics were not found was that they were simply destroyed.
Whether the Viking landers detected life on the surface of Mars is still an open question.
The only way to solve that mystery is to go to Mars and experiment some more.
This will no doubt happen in the coming years as the human exploration of Mars becomes a
reality.
Number 9.
Formaldehyde
In 2005 the European Space Agency’s Mars Express orbiter detected a rather odd chemical
in the atmosphere of Mars.
It’s formaldehyde.
We normally think of this chemical as a constituent of embalming fluid, and a carcinogen.
But there’s more to it than that.
We see formaldehyde in the universe, and interstellar formaldehyde has been studied extensively
within the milky way.
And for good reason, it’s an organic compound.
In the case of formaldehyde in the atmosphere of Mars, it’s possible that it could be
a by product of the oxidation of methane.
This would suggest that Mars is very geologically active, but we don’t really see that it
is.
It’s major volcanoes appear long dead, and what may be occuring doesn’t seem too active.
The other option is that it’s a product of microbial life.
But this is a pretty ambiguous indicator, in the end.
8.
The Lichen that Could Survive on Mars
One of the ways we have of understanding if there was, or is life on Mars is to look at
very resilient species of organisms here on earth, simulate the conditions of Mars, and
see if they could survive.
While a number of resilient bacteria from earth have been shown to be able to survive
the conditions expected at shallow levels in the soils of Mars, one organism stood out.
It was an antarctic lichen.
Known as P. chlorophanum, it survived temperatures as low as -51 celsius, low atmospheric pressure
like that of mars, and endured large amounts of radiation during a 34 day experiment.
The lichen fared well enough that if it had some protection against radiation, such as
living under a rock or in a crack, it might actually be able to survive on the surface
of Mars long term in an active state, and in fact, it adapted to the conditions and
ramped up photosynthesis as the experiment went one.
In other experiments involving lichens, they’ve shown themselves not only capable of handling
Mars, but clinging to life in space itself.
Lichens might also survive things like Mars’ global dust storms by going into a dormant
state, something that some earth lichens can do on the order of centuries if covered in
snow or dust.
This one has two implications.
Firstly, if Mars ever developed life like this lichen, then that life could still be
there surviving in cracks or beneath rocks.
Second, we should be careful with what life we transport to Mars, even accidentally, because
some of it could in principle survive and contaminate that planet.
7.
Oil on Mars?
One of the strangest possibilities is that if Mars once had, or still has, microbial
life it may be possible that the process that produced crude oil deposits on Earth, might
also have occurred on Mars.
On earth, crude oil deposits are thought to be produced when marine microorganisms die
and become trapped in sedimentary deposits.
As this becomes sedimentary rock, heat and pressure converts the material into petroleum.
While the origin of petroleum is somewhat controversial, in the case of Mars, it might
have been possible for oil to form from any microorganisms that were present in the past,
or in an alternate hypothesis trapped hydrocarbons left over from the formation of the solar
system, and have crude oil deposits.
In principle, these should be detectable as methane emissions, effectively natural gas,
and through geologic exploration of Mars.
And maybe, some day, an oil rig.
6.
The Reanimating Corpse Planet
This is more of a concept than an indicator, though if it were to happen it would provide
a perfect opportunity for observing life on Mars from here on earth.
One of the things that makes the surface of Mars inhospitable to most life as we know
it is the high amount of ionizing radiation that reaches the surface.
But this changes.
Due to Mars’ orbital eccentricity and the tilt of its axis, it may be that Mars goes
through periods, the most recent about 450,000 years ago, where the dormant surface life
on Mars hidden beneath the surface might reanimate and recolonize the surface for a time.
A sort of periodic Frankenstein planet that reanimates periodically and resembles its
former self.
If this is the case then that dormant life might still be viable, and detectable as shallow
as one meter below the surface.
Future missions to Mars might look there and see what they find.
Number 5.
Martian Geysers
Mars southern polar cap is in a constant state of frosting and defrosting seasonally.
Because of this, C02 and likely water can pressurize beneath the surface and erupt as
a geyser, usually in the form of cold fluids mixed with mud.
This process happens rather quickly, even by geological standards here on earth, which
makes it very odd for sleepy Mars.
Around these guysters, dark spots and channels can be seen that are not well understood.
One team has proposed that they represent photosynthesizing microorganisms.
The idea is that these microorganisms hibernate while the southern polar cap is in darkness,
as the sunlight returns however light reaches the ice, and the organisms beneath.
As they start to photosynthesize, they produce heat and liquid water, which is trapped under
the ice and cannot evaporate.
The sun then further melts the ice and the microorganisms appear grey.
But as soon as the ice melts completely, they dry out and turn black, creating the dune
spots.
While this remains a possibility, it could also be something entirely geological that
forms the dune spots.
Only by going there with a probe will we answer the question definitively.
4.
Curiosity and Complex Organics
In the summer of 2018, NASA’s Mars Curiosity rover at Gale Crater on Mars was studying
roughly 3.5 billion year old mudstone rocks.
Within these rocks something was seen that hadn’t been seen on Mars before.
Large concentrations of organic chemicals, essentially the missing organics that the
Viking landers had failed to detect.
They came in the form of very complex organic molecules thought have been preserved due
to the presence of sulfur.
Even stranger, this mix of chemicals resembles what happens when kerogens break down.
Kerogens are interesting because they are of biological origin here on earth, and in
fact are a precursor to crude oil.
But resembling does not make for a dead ringer.
Just a hint that life may have been responsible.
3.
Fossilized Bacterial Mats on Mars?
Life leaves its mark on planet earth in many ways, ranging from the oxygen in our atmosphere
to the fossils of shells one might find eroding from a mountainside.
But even the smallest life, the bacteria, do leave traces of themselves.
One such trace are fossilized bacterial mats that show the actions of bacterial colonies
millions of years ago.
Here on earth these mats form in areas of shallow water, such as lakes or coastal areas.
If the mats are undisturbed, they can fossilize, and in fact may represent some of the oldest
fossil evidence of life on earth, with one formation in Australia yielding examples that
are as old as 3.48 billion years.
But Earth is not the only place where potential fossilized bacterial mats have been seen.
There are candidates on Mars photographed by NASA’ Curiosity rover.
Present are domes, roll ups, pits, and other indicators in the sedimentary rock that looks
much like they look here on earth.
More, mats here on earth change as they dry up, rebound, and so on.
This appears to also be the case with the structures on Mars.
The rocks look eerily similar.
Unfortunately to go much further with this one, we would need a sample return mission
to bring samples of the sedimentary rock to earth to be studied in the lab.
This is unlikely to happen any time soon.
Number 2.
The Martian Meteorites
It may surprise you, but we actually have pieces of Mars right here on earth in the
form of meteorites that originated on the surface of that planet but were blown off
and into space during large impacts.
There are currently over 100 known examples of meteorites that show geologic and chemical
evidence indicating a Martian origin.
Some of these rocks may indicate the presence of past life on Mars.
This is a controversial topic, and no consensus within science has formed around just what’s
going on with certain features of these meteorites.
At one point, it was even announced by then president Bill Clinton that evidence of life
had indeed been detected in the Allan Hills 84001 meteorite.
This was called into question by other researchers, but it’s an interesting factoid that the
only government to have ever announced evidence of the existence of extraterrestrial life
in an official capacity was the US government under the auspices of NASA.
And, they jumped the gun and announced it too early, only for it to be called into question.
Wrap your minds around that one conspiracy theorists.
The first of these meteorites is the aforementioned Allen Hills 84001.
This meteorite was found in Antarctica, and in 1996 it was reported that microscopic features
along with geochemical anomalies may indicate evidence for past life in this meteorite.
The problem was that this life was very small, far smaller than earth microbes.
And as the story unfolded, it became clear that non-biological processes could explain
all of the features seen with the rock.
But life could also have been responsible, so the question to this day remains up in
the air.
Another example is the Nakhla meteorite, which fell in Egypt in 1911.
With this meteorite, evidence of what look like nanobacteria again were found.
Further they found organic chemicals within the meteorite that might be life related,
and they further found that most of it probably isn’t recent earthly contamination, but
actually from Mars.
But carbon is a common element, and you don’t need life for it to exist, in fact the opposite
in earth’s case with its carbon based life, so no dead ringer here.
Two other meteorites that show anomalies are the Shergotty and Yamato 000593 meteorites.
Shergotty shows what appears to be alteration by water, before it arrived here on earth.
Fragments of this meteorite were picked up almost immediately by residents of Shergotty,
India, as it was an observed fall, so this is a very pristine example of a Martian meteorite.
Within it, what appears to be a biofilm associated microbes has been reported but more work on
this meteorite needs to be done before anything conclusive can be said.
With Yamato 000593, this meteorite is effectively a lava rock, a basalt that formed on Mars
about 1.3 billion years ago.
There it sat until about 12 million years ago when it was ejected in an impact.
Evidence of exposure to liquid water before it fell to earth is present in this meteorite,
but also there are bizarre spheres of carbon found inside it.
But only in certain parts of the rock.
Biology being responsible for this is on the table, but again, it’s far from conclusive
evidence.
Number One.
Methane
The biggest hint that something life related may be going on at Mars is the gas methane,
which is a gas that life on earth produces.
Mars’s atmosphere makes methane chemically unstable, the ultraviolet radiation streaming
off the sun, and the chemistry of Mars’ atmosphere quickly destroys methane.
This means that if Methane is present on Mars, it must be replenished by some process, either
geological or biological.
Methane has indeed been detected on Mars.
And the source of that methane is rather mysterious and tantalizing.
We’re not talking about a lot of methane, which was first detected on Mars in 2003.
But, as study continued, it became clear that the methane was concentrated in certain areas
on Mars, and more provocatively appears to be seasonal.
Seasonal methane releases could be produced geologically, but we also know how seasonal
changes impact life here on earth, and the lack of obvious volcanism and hydrothermal
energy on Mars would be a point against geology.
Bolstering this were observations from June of 2019 by the Curiosity rover which detected
unprecedented levels of methane being released.
While it’s still not clear if it is biological in origin, it could be that methanogenic bacteria
very similar to the earliest life on earth could still be active on Mars deep below the
surface where liquid water is still possible.
Once again, only human exploration is likely to answer the question.
Thanks for listening!
I am futurist and science fiction author John Michael Godier currently envision oil rigs
on Mars.
C02 emissions will actually help Mars to warm back up, so instead of electric Mars rovers,
we’ll need fleets of gas guzzling LeBarons.
And, later this week on Event Horizon I will be speaking with Dr. John McGowan who wrote
the paper on the possibility of petroleum fields on Mars that he wrote back in the year
2000 while at NASA Ames, links to the paper and the interview below and be sure to check
out my books at your favorite online book retailer and subscribe to my channels for
regular, in-depth explorations into the interesting, weird and unknown aspects of this amazing
universe in which we live.