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.
