Many people care deeply about the possibility of tigers, lemurs and such like becoming extinct in the wild. I'd like to suggest we care as much about the possibility of microbes on Mars becoming extinct. And more so.
So what's so special about microbes on Mars? Well first, the uniqueness. Tigers are closely related to cats. They are wonderful and remarkable creatures - and would be a tremendous shame to lose them - but basically it's the familiar tabby in another guise.
For microbes on Mars though - the most interesting possibility is that they may be unrelated to any living organism on the Earth. Think not so much a microbial version of a tiger - but a microbial version of ET.
A young adult tigress from the Terai in India - Sumeet Moghe
HaloBacterium Salinarum - isolated from Lake Zuf in Wadi Natrun, Egypt - recently genetically sequenced - Microbes like this could exist on Mars.
Microbes on Mars, in the more interesting case, would be more like a microbial version of ET than a tiger
Mars could be an exoplanet in our own solar system - for biologists.
You may know that we have discovered many exoplanets in the last few years. Cool visualization of them here:
Exoplanets orbits
All superimposed, on one orbital plot - according to orbital periods and dimensions - cold ones blue, hot ones red, possibly habitable ones green.
They may all have life, or some, or none.
But one thing they all have in common - they are light years away from the Earth. There is no way that we will visit them in the near future, unless we develop warp drive or some such. Chances of sending a rover to explore them, and to get information back to Earth within our lifetimes is remote indeed.
Mars though is right here in our solar system. It might be the only opportunity we'll get in our lifetimes, or in the next few generations, to meet microbial ETs up close on an Earth like planet. And it's the only chance we have to examine life on a planet that was a near twin to Earth in the early solar system, and shared the same solar system as Earth.
INTRICATE DETAILS OF LIFE ON EARTH - HOW UNLIKELY THAT UNRELATED MICROBIAL ETS WOULD RESEMBLE OUR MICROBES CLOSELY
HALF OF THE PAGES OF BOOK OF EVOLUTION HAVE BEEN TORN OUT
HOW LONG DID IT TAKE FOR THE FIRST ARCHAEA TO EVOLVE
Well according to one estimate, the history of the Earth is not long enough for them to evolve. These researchers plotted the increase of complexity of non redundant nucleotides in DNA. As life increases in complexity, it follows a near straight line on this log plot, through many different changes of structure of organism, from the prokaryotes, to the Eukaryotes with nuclei, worms, fish, and mammals
They traced the timeline back, expecting it to cross the zero line at the time of origin of life, and found that the zero line is nearly ten billion years ago, over twice the history of the Earth.
This diagram shows the complexity of the DNA as measured using the number of functional non redundant nucleotides.This is a better measure of the genetic complexity of the organism than the total length of its DNA. Some microbes have more DNA than a human being - much of that used for other purposes rather than for genetic coding, the so called C Value Enigma. Measuring it this way deals with that issue.
Notice that the prokaryotes are well over half way between the amino acids and ourselves.
They tentatively suggest that this might be evidence that life on Earth actually originated around other stars, and was transferred into the early solar system as the nebula condensed by meteorite impact transfer (for instance another star with a life bearing planet passing through the condensing solar nebula could do that).
If that's right then we might expect life to be abundant in our early solar system, as Mars must surely have been infected by this life just as Earth was, and share DNA etc. All life might be based on DNA (or you might get a hybrid situation where some primitive XNA based life also evolves in favoured spots in the solar system).
The other possibility is that life evolved far more quickly in the early solar system than the log plot suggests. For instance, it was probably not DNA based back then, and that might make a difference. If so then we might find pre-archaea on Mars.
If so, their study usefully highlights quite how much evolution was needed to get from there to the modern archaea. Judging by nucleotide complexity, you'd expect that as many stages of evolution were needed to get from non living chemistry to the early archaea, as were needed to get from the early archaea to modern mammals.
Also looking at this another way, it's a huge increase in complexity from 10s of nanometer scale cells to the hundreds of nanometer scale modern cell already present in the most primitive archaea, with DNA, RNA, transcriptase, enzymes, proteins, and maybe a million different chemicals operating together to keep the cell alive and functioning. This modern cell transcription mechanism, chemistry, cell walls and metabolism might well have taken hundreds of millions of years to develop.
The first primitive cells were surely far smaller and can't possibly have been as complex as this. Perhaps they used only a few different chemicals.
So, wherever the life originated on Mars, it might well have taken some time for it to evolve from the primitive tens of nanometer cells to robust forms of life that could adapt to other conditions. So, it might well have remained in that habitat for some considerable period of time, maybe for most of the Noachian period or longer.
HOW FUNDAMENTAL LIFE PROCESSES ARE FOR TECHNOLOGY, MEDICINE, AND OUR DAILY LIVES
WHAT WE COULD FIND ON MARS - FIRST POSSIBILITY - EXOPLANET LIKE MICROBIAL ETS
SECOND POSSIBLITY - VERY EARLY MICROBIAL FORMS LESS DEVELOPED THAN EARTH LIFE
THIRD POSSIBILITY - MODERN LIFE THAT SPLIT OFF FROM EARTH BEFORE THE MODERN CELL MACHINERY WAS COMPLETEY ESTABLISHED
FOURTH POSSIBLITY - MODERN LIFE - BUT DIFFERENT CAPABILITIES E.G. DIFFERENT PHOTOSYNTHETIC PIGMENTS OR METABOLIC PATHWAYS
FIFTH POSSIBLITY - NO LIFE THERE - BUT PREBIOTIC CHEMISTRY
SIXTH POSSIBLITY - IN ALMOST ALL WAYS IDENTICAL TO MODERN EARTH MICROBES
SEVENTH POSSIBILITY - PERHAPS MOST LIKELY - A MIXTURE OF SEVERAL OF THOSE VARIOUS POSSIBLITIES
IF INTERESTINGLY DIFFERENT LIFE IS FOUND ON MARS, CHRIS MCKAY'S IDEA TO "MARS FORM" MARS
OR COULD RECREATE EARLY MARS (EVEN IF NO LIFE IS FOUND)
This might help us learn a lot about evolution - how easy or hard it is to get started - how far it gets - prebiotic process and situations on other planets in our galaxy
OR COULD LEAVE MARS AS IT IS IN PRESENT PRISTINE STATE, FOR NOW
COULD WE PRESERVE PARTS OF IT ONLY? - HARD TO SEE THAT WORKING
FUTURE PRESSURE ON MARS
So far, we have taken reasonably good care to keep invasive species away from Mars. But with pressure mounting for human missions to Mars, there's some pressure to reduce the level of protection. It's done on the basis of probabilities. As we can't sterilize our spacecraft completely, they are sterilized enough to reduce the chance of introducing life to the solar system to less than 1 in 10,000 for each mission.
Should we care more about microbes that may exist on Mars, or about the humans who have a keen wish to walk on Mars in person?
No-one complains about the need to keep invasive species away from islands with unique lifeforms. We know that they are one of the major causes of extinction of species. In the case of birds, they are right at the top of the list.
Major threats contributing to extinction to species of birds since 1500
