New Evidence For Ancient Life On Mars

siddesu writes in with "compelling" new data that chemical and fossil evidence of ancient microbial life on Mars was carried to Earth in a Martian meteorite. The finding is being highlighted by the same NASA team who made the initial discovery 13 years ago. Spaceflight Now has more details of the analysis.

Comments

Panspermia

[jpmorgan]

I'm rooting for panspermia. There's something kind of cool at looking at Mars and thinking: that's where we came from, and the rovers are just us coming home.

Re:Panspermia

[jc42]

It could be hit and miss. Just because fossil evidence got here doesn't mean anything living made the trip. But, it does open up a lot of questions. If the Mars microbes didn't make it, that doesn't mean something else didn't. We'll figure it out in a few centuries, ...

Actually, astronomers figured it out a few decades ago. They concluded that, while the Mars -> Earth trip is difficult and unlikely, the other direction has happened with probability around 0.999999.... The mechanism is the Earth's "dust tail", a stream of gases and dust much like a comet's tail, but even thinner. It is thick enough to cause a problem for some astronomical observations, though, which is why some astronomers studied it during the 1960s and 70s. They found that the tail includes "dust" as large as bacteria, and since high-altitude airplane and balloon samples had shown bacteria at all altitudes, our default assumption should be that there are bacteria (mostly in spore form) in our planet's dust tail. This wouldn't be a million-year trip. The solar wind blows Earth's dust tail outward along the plane of Earth's orbit. It would sweep over each of the outer planets about once per year, contaminating each planet with bacterial spores in each pass.

So if we find life on any outer planet that is chemically similar to bacteria here, we can't conclude anything about where it originated, except that the most likely source is Earth. It could have reached Earth from the outside, of course, and is just making the return trip.

A fun part of these studies was the conclusion that this thin stream of bacterial spores does eventually get blown out of the solar system. Distances out there are large, of course, but if you look at the numbers, you find that the Earth takes roughly 4 trips around the galaxy every billion years. Since the earliest known bacterial life developed here, we've made 15-20 trips around the galaxy, spewing bacterial spores along our path the whole time. Chances are that they've pervaded the entire galaxy (very, very thinly). If they can survive the millions or billions of years in interstellar space, then we're one of the sources for the panspermia hypothesis.

Of course, the astronomers didn't know anything at all about the survivability of bacterial spores in space. We still don't know much about it. That's the weak link in the whole guessing game.

But it's highly likely that there are bacteria living underground on Mars, and they came from Earth. It would be a lot more fun if we found some there whose biochemistry was different from the micro-organisms on this planet.

(I googled for this topic a couple of years ago, and didn't find much of anything. I wonder if there are any astronomers here who could point us to more details.)

Re:Panspermia

[Tablizer]

And you were able to deduce all this from the presence of a "worm-like" object associated with a meteorite?

No. It's from various studies of Mars. It's had almost a dozen successful orbiters and 5 successful landing vehicles on it. There is plenty of evidence that Mars was once much wetter.

It also comes from knowledge of Earth. Our atmosphere and water is largely protected from space radiation due to our magnetic field, which based on commonly-accepted theories is generated from currents within Earth's semi-liquid-metal core. The field acts as a radiation shield.

Bigger planets take longer to cool. Mars, being about half the diameter of Earth cooled off much quicker, it's core now almost solid (or at least stationary). All planets and large moons had a hot core at one point in time soon after formation, and thus probably also had a magnetic field (assuming sufficient metal content). The difference is in part how fast the core cools, which is largely a function of body mass. (It's expected that Earth's magnetic field may give out in a couple of billion years.)

In fact, Mars' ancient magnetic field left slight magnetic patterns in rocks, almost like tape-recorder tape, which can be detected from orbiters. This tends to confirm that Mars once had an ample magnetic field also, explaining how all that water was able to stay on the surface. A thick enough atmosphere allows water to stay liquid and not evaporate into space via ionization.

Also, the cratering rate of the solar system has been estimated and modeled from studies of the moon. Based on these rates, one can estimate the age of various larger-scale surface features of Mars using crater density. If you know the rate of bombardment throughout history, you can estimate the age of surface features. It's sort of like estimating the age of a car by looking at the pebble nicks on the front bumper.

Sure, it could all be wrong, but it's the model that currently best matches the evidence: Mars used to be "nice".
     

Re:Panspermia

[Tablizer]

[If] life on Mars and life on Earth share a common history, it makes it much easier to muck around on Mars, because it'll just be another extension of life here so no worry about contamination.

That may not be a safe assumption. When Earth organisms go into new environments on other parts of Earth, they often encounter microbes they are not accustomed to, and become ill or die. It could be a big risk.

If ANY life on Mars is found, regardless of origin, it may be best to leave it alone. Send only one-way labs or colonies to Mars. Don't risk the sci-fi Andromeda Strain come real.
   

Oh wow

[Dartz-IRL]

It's life.

Or was life.

If this is true. It's just staggering to me. If there was life on Mars.... there may still be. If there was life on Mars, then how common is life elsewhere in the galaxy? If it can exist on ancient Mars, there's no reason it can't exist on any of the other millions of planets scattered through the billions of stars in our Galaxy.

If life is found on Mars... or found to have existed.... then it can be anywhere.

Under the ice of Europa aswell?

While we may never meet our neighbours..... it would still be nice to know that yes, they may well be out there.... somewhere. The Galaxy may well be teeming. I sure hope it is. I mean, if it becomes clear that rather than being just blacks, whites.... whatevers.... on a cosmological scale where there is actual non-terrestrial life.... shouldn't it be clear that we all are just the one race?

Re:Well

[wizardforce]

As a iochemist, it was my understanding that the habitable zone was already known to extend out toward Mars. Although really, I'd say that the concept of a habitable zone needs to be expanded anyway considering the possibility of life in the Jupiter system. I believe that it is becoming increasingly clear that there isn't just a single habitable zone around a star like our sun but also pockets of habitable space underneath the surface of various moons and terrestrial planets like Mars.

Re:Well

[Kjella]

As a iochemist, it was my understanding that the habitable zone was already known to extend out toward Mars.

Well. there's a difference between being potentially habitable for a species, and finding remnants of actual life. Either life appear on both Earth and Mars independently, meaning there's actually a quite wide band of possible conditions - or life really transports across space. Either way is much more compelling arguments for the habitable zone actually being habitable than a theoretical zone based on temperature.

Re:Well

[lena_10326]

or life really transports across space

Humans are generally considered a form of advanced life and we've transported ourselves and microbes across space. The thing I don't understand is why it's such a wild and crazy concept to consider the possibility of advanced life traversing space from Mars to Earth millions or billions of years ago.

Either way is much more compelling arguments for the habitable zone actually being habitable than a theoretical zone based on temperature.

If it isn't already, the habitable zone should be stratified into layers indicating habitable for humans down to microbes. Some people are only interested in discussing habitable for humans while others think more expansively. Thinking in layers would clear up any confusion.

I propose using alphabetical labels. An "A" class for single cell organisms, "M" class for humans, "Z" class for .. hmm.. not sure yet.. maybe beings requiring hot conditions under high pressure.