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

[danlip]

I'm rooting for independent evolution. It would make it far more likely that the universe is teaming with life. But unless we find current life on Mars, it may be hard to tell the difference.

Re:Panspermia

[Anonymous Coward]

Either case means the same thing, that life can travel and spread. It takes millions of years for a rock from mars to reach earth, and vice versa. If life can survive that journey, why couldn't it survive in some small way between stars, over billions of years.

If life once existed on Mars, it will exist now. It is highly unlikely the entire planet became 100% sterile. There will be pockets of life surviving the harsh climate.

The big question is exploration of Mars. If life evolved independently, we will have a much harder time mucking around there, especially colonizing it. Folks will want to leave it alone to its own devices. It 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.

Re:Panspermia

[Tibia1]

It's going to be funny when they find a fossil of an ancient rover on mars.

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

[c6gunner]

Either case means the same thing, that life can travel and spread

No, they don't mean the same thing. If life began once and was seeded via meteorites, then it's a giant crap-shoot, and the vast majority of solar-systems are probably sterile. On the other hand, if abiogenesis took place twice in a single solar system, then the universe is probably teeming with life.

If life evolved independently, we will have a much harder time mucking around there, especially colonizing it. Folks will want to leave it alone to its own devices.

Hardly. It might raise some ethical conundrums, but it certainly won't make colonization any more difficult.

If we ever colonize mars, we're going to start by building habitats. We'll have hundreds of years to live on a planet which we haven't even begun to terraform. That will give us plenty of time to have the People for the Ethical Treatment of Martian Lifeforms present a convincing case for why we should abandon an entire planet to a bunch of alien microbes. If they fail in convincing the rest of humanity, then we'll carry on with our terraforming effort, and the Martian bacteria will be relegated to sample jars, museums, and computer databases.

Re:Panspermia

[Tablizer]

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....

Mars-to-Earth is 100% because we found a dozen or so meteorites from Mars, proving it happens. (Kudos to Viking Landers for the chem analysis to compare.)

Because of Earth's size compared to Mars, Earth was still a hot coal when Mars was almost like Earth today, with mild temperatures, relatively thick atmosphere, and lakes, possibly even oceans. Thus, life is more likely to have had evolved on Mars early in the solar system's history than Earth, if it was around then. Mars was the happening club in town back in the days.
   

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".
     

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:Mars origin

[wizardforce]

Can someone explain to me why the set of meteorites are considered more likely to have originated on Mars than from an impact on Earth itself?

Gas bubbles found in the meteorite have a composition that is very much like the atmosphere on Mars. The gas inclusions don't resemble those of Earth.

Re:Mars origin

[MichaelSmith]

TFA:

Scientists were able to trace the meteorite back to Mars, as its chemical composition matched the relative proportions of various gases measured in observations of the atmosphere of Mars made by the Viking spacecraft in the 1970s.

Re:So here we have spent huge amount of resources.

[ianare]

If it wasn't for the spacecrafts sent to Mars, it would not have been possible to identify the meteorite as coming from Mars. From the article : "Scientists were able to trace the meteorite back to Mars, as its chemical composition matched the relative proportions of various gases measured in observations of the atmosphere of Mars made by the Viking spacecraft in the 1970s."

As for the rovers sent later, they were not sent to investigate life but mainly to study the geology and climate.