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.

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: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.