The search for life on other planets could get a boost from biosignatures

L A Times ^ | Jan 24, 2018 | 3:25 PM | Amina Khan

[BenLurkin]

Scientists have focused on a few potentially telltale molecules, such as methane. Methane is produced in large quantities by microbes on Earth (including those in the bellies of cattle). But methane can also be produced by nonbiological sources, such as volcanoes.

Molecular oxygen (two oxygen atoms bonded together) is produced in massive amounts today by photosynthesizing algae, plants and microbes. But the photosynthetic mechanism is so complicated that scientists think it evolved only once on our own planet. That means there's no guarantee of finding oxygen-producing photosynthesis on other worlds, even if life does exist there.

Thus, relying on any individual chemical could produce false positives or false negatives, said study coauthor Stephanie Olson, an astrobiologist and graduate student at UC Riverside. But living things alter their environments in complex ways. What if there was a particular mixture of molecules that would not exist without life?

To find out, Catling's graduate student Joshua Krissansen-Totton led a study that examined the Earth's atmosphere in three stages of its existence: The Archean (4 billion to 2.5 billion years ago), the Proterozoic (2.5 billion to 541 million years ago) and the Phanerozoic (541 million years ago to the present).

During each of these time periods, life (and the planet itself) looked very different. Place a snapshot of each Earthly period side-by-side, and they'd look like totally different planets.

"The phrase Earth-like does not refer to a planet that necessarily resembles modern-day Earth at all," Olson said. "It's actually a very broad term that encompasses a broad variety of worlds. It includes hazy worlds like the Archean; it includes icy worlds like the 'snowball Earth' intervals; it includes anoxic worlds with exclusively microbial ecosystems; it includes worlds with complex and intelligent life; and it includes worlds that we haven't even seen yet."

[blackdog]

Silly me. I thought it was about finding blue dresses?

[faithhopecharity]

How about a search for intelligent life in the DNC?

[WMarshal]

If life is so special and unique to earth we should be seedng the solar system with it.

[Getready]

Highly conjectural suppositions.The writer of article does not seem to be very well versed on basic chemistry or biology.

[LouieFisk]

“Methane is produced in large quantities by microbes on Earth (including those in the bellies of cattle)”
—
So basically they’re gonna look for little green men with major flatulence issues.

[Getready]

Also produced in bellies of humans....duh....

[Getready]

La times writers gotta be completely clueless bout biology and chemistry...where do they get those writers?...any penetrating questions in your ipad? la times should be renamed...”NEWS FOR DUMMIES” written by one of your own..

[rightwingcrazy]

“It’s actually a very broad term that encompasses a broad variety of worlds. It includes hazy worlds like the Archean; it includes icy worlds like the ‘snowball Earth’ intervals; it includes anoxic worlds with exclusively microbial ecosystems; it includes worlds with complex and intelligent life; and it includes worlds that we haven’t even seen yet.”

I’m trying to imagine what “we haven’t seen yet” after reading such a breathtaking list of worlds that we apparently have already seen. Including those with intelligent life. Like Vulcans, I guess.

[blackdog]

So to send a signal to other world that we are here, we need all those bad greenhouse gasses. Just following logic.

[Crucial]

I think assuming that life on other world wouldn’t develop photosynthesis, taking advantage of the boundless energy of a nearby star is ludicrous.

[dead]

But the photosynthetic mechanism is so complicated that scientists think it evolved only once on our own planet.

That’s some jackassery masquerading as science. I think the author of this article is in over his head and misunderstood something a scientist told him.

[DungeonMaster]

Idolatry: Searching for life on other planets, among other things.

[Moonman62]

Molecular oxygen (two oxygen atoms bonded together) is produced in massive amounts today by photosynthesizing algae, plants and microbes. But the photosynthetic mechanism is so complicated that scientists think it evolved only once on our own planet.

...

Think about that and what it means for how rare life is.

[Moonman62]

Nope. Photosynthesis appears to be an evolutionary singularity. Abiogenesis is, too. The appearance of eukaryotes would be another one.

[dead]

How could anybody make that case with a sample size of exactly one life-bearing location?

[Moonman62]

Do you mean photosynthesis occurring on other planets?

[dead]

Yes, I see that the sentence could mean it only happened once as far as earth is concerned. I took it to mean it only occurred once anywhere and happened to be on our planet.

What mechanism would reveal it to be a singular event in earth history? Seems like a speculative call.

[Moonman62]

Many years of study indicate that all photosynthetic organisms are related to each other, so that they all have a common ancestor, and they are all on a single branch of the tree of life.

Then there are articles like this that indicate geologic evidence, too.

http://www.dailygalaxy.com/my_weblog/2013/07/great-oxidation-event-a-new-discovery-of-evolutionary-singularity-that-transformed-the-planet.html

[SunkenCiv]

Thanks BenLurkin.

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