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The Biology Book: From The Origin Of Life To Ep...

Greetings, friends of astrobiology. Welcome back to a new episode of Ask an Astrobiologist. This program is the show of the website, where we celebrate science, diversity in science, and scientists. This program is made possible by contributions from the NASA Astrobiology Program, ELSI, the Earth-Life Science Institute, and the nonprofit Blue Marble Space. My name is Sanjoy Som, but before we start, this is your background quiz, like every month. Mike, if you could put up the background from last month. It is, actually nobody got it right, there was no suggestions for what it is.

The Biology Book: From the Origin of Life to Ep...

I was asking you guys to kind of identify what the little mounds were on the bottom left of the image. Those are actually modern stromatolites. Those are microbial mats that grow up towards the sunlight, of course, and they form mounds. They're modern analogs of some of the most ancient fossils of life we know on Earth. The ones from the background from last month are in a biological reserve in Mexico, called Cuatro Cienegas, if I pronounce it right. Some of the oldest ones we have found in the fossil record are over 3.5 billion, and that's with a "b," years old. So really really ancient forms of life that are found today in analog environments.

Oh, yeah, of course. Even Mars last year, I think 2015, maybe it was, the finding of organics on the surface by the Rovers. The paper, I think it was the Journal of Geophysical Research, a big group, said that, well, the organics that we're finding are probably either meteoritic or from some indigenous Mars process. As I say, how the astronomers see these compounds, every place they look, and now obviously land on Earth every day, or we wouldn't have them, the rocks in our labs. But now on Mars, years ago, we saw a comet crashing into Jupiter, so yes, the potential, in addition to the meteorite organics, the further chemistry on Earth, or maybe some also indigenous Earth compounds. Yeah, I think there's a great potential for other life.

Well, we had an outreach the other day with students from one of the high schools, somewhat sort of local high schools, and I had powder that is no longer used for research, meteorite powder that we grind up and extract out the organics. But what I did was let them smell it, because if you shake it, the particles are still breaking down to this day, and the original gases from the solar system come out. Most students say it sort of smells like dirt, maybe wet dirt in the country when you walk along the road.

You bring up a good point, in the sense that Earth is covered with biology, right? If a rock from space falls on the planet, then the biology that's near it could contaminate it. How are we sure that these organic matter that we find in meteorites are not just Earth contaminating the rock?

It would make glycine with two carbons, all the way up to ... The space process is abiotic, non-biological process, would make from carbon number 2 to carbon 15 for amino acids. It's just thermal dynamics, whereas life on Earth uses very specific amino acids, very specific weights. Life, your body, bacteria doesn't want to make every possible isomer of a compound up to C-10. There's simply, that's a waste of energy. Again, the nonbiological, abiotic process in asteroids, probably comets, make all, including weird ones not used. That's how you tell if it's really from space, is nonbiological compounds.

That's so cool. Meteorites are really the history book of the solar system, and you and your colleagues learn the language of the rocks, really extract the story of what that means for the formation of planets, but also for the origin of life. It's just a fascinating field. Many years ago, I was lucky enough to be in Washington, D.C., and was visiting the meteorite collection you were talking about, and I held in my hand ALH 84001, which is like the meteorite that we know came from Mars. There's not only meteorites that come from far beyond in terms of asteroids that feed the Earth, but also the different planets are exchanging rocks with each other. Have you worked with Martian or even lunar samples?

Well, I came to Ames as a postdoc for Sherwood Chang, who's one of the founders of astrobiology. He really worked for years to focus research, get funding for research, and he was the branch chief at that time of the exobiology branch here. He retired years ago. I was his postdoc, so a few years postdoc, and then a position came open, I was lucky to get the research scientist position here. That was pretty much just the trail from graduate school.

Maybe in three years, I'll give you an answer. But that's the golden question, you know. We see the compounds, organic compounds in meteorites, but it's obvious that it took from there some more, some additional chemistry on the Earth. For example, right now, we don't see long polymers of proteins, you know, made of amino acids, which is in everything that's life. There's a very small two amino acid peptide, very small piece of a protein, but that's in very trace amounts. It had to take more chemistry from the Earth, and probably additional chemistry in hot regions. People are doing hydrothermal vent simulations, people like George Cody at Carnegie.

Yeah, it's an active area of research. If I understand you well, the seeds you need to get life started on a planet requires not only solar system chemistry, where you have cosmic radiation that's interacting with ice in the meteorites to create this organic matter, but also the geochemistry, the chemistry that's happening at the interaction of a hot terrestrial or planetary surface, interacting with rocks and water and the chemistry that's happening then, putting those two together, and with the proper conditions, could then arise biology, right? So it's not only a closed planetary ecosystem that leads to life, it's this interaction of the planet with its outer solar system environment.

That's so cool. I could talk to you forever about meteorites and organic matter, but I think it's time that we opened the floor up to questions. I'm going to turn to my question screen, which is right here. The first question is from Michael Wong: "What is responsible for choosing the chiral 'handedness' of organic molecules in life?"

Most people from school, high school, have seen the long strands, you have an RNA, a base and phosphate, and it repeats. RNA, ribose, phosphate, base, and it goes on and on and on. But only one of those ribose, only the D mirror image is used. That's what caller Mr. Wong is asking about, how in the world can you get just one? Because if you go in the lab to make, let's say ribose, nonbiologically, like what happened before life, it wasn't a biased process. If you go in the lab now, and do the same thing, you'll get both. You'll get two hands, just like flipping a coin a thousand times. You can't get one coin, only heads.

Lately we see sugar derivatives, cousins of ribose, that has a lot more of one mirror image, and that's the D mirror image, and maybe it's coincidental now, but the D of the sugars is what life uses mostly. Is that a hint to the answer to that question? What else happened on the ancient Earth? That, what I described came from space, comes from space, what else happened on Earth? People are looking at that. Maybe if this worked, we could do more of it, and see the same thing over and over. I saw that phenomenon since 2001, but we just published it, but I've seen the same phenomenon in these sugar derivatives for over 15 years. People wondering, why the heck aren't you publishing it? You still, I still, you should still look at it in different ways.

There are so many questions that are pouring in right now. Thank you all for all these great questions. We're probably not going to have time to get through all of them, but we'll do the best we can. What is the next question here? Oh, it's a question by Jacob Haqq-Misra. Hello, Jacob, thank you for your questions. He asks, "What are the main geochemical differences between meteorites that originate from Earth compared to from Mars?"

Okay, well, going back again to before I started, and I mentioned the '97 paper, Cronin and Pizzarello. Before that, there was a paper looking at biological amino acids. Ingall and Mackell, and I forget the year, around 1990, of alanine, a biological amino acid. Again, people are always leery of biological, if you say there's an enantiomeric excess, but it was good work. We'll have to see about more about the biological amino acids. When you get to the '97 paper, Cronin and Pizzarello, as I said, some of the strange amino acids that are not in biology, that's there's no question that they came from space, so if you see an enantiomeric excess, you can say that's indigenous for a fact.

I just want to give the opportunity of having one last question before we end. That is, Damian Sternmann, hi Damian, thanks for your question. He is asking perhaps a more speculative question, because life on Earth and life on other terrestrial planets probably came from the same building blocks. He asks, "Do you think, and speculatively, would alien organisms also use peptides and DNA and similar stuff that we're made of?"

Even though so many uncertainties about life and information remain, the information-theoretical analysis convincingly highlights the extraordinary power of life: While information is both enormously valuable and exceptionally rare, the simple act of copying (possibly with small modifications) can create information seemingly for free. So, from an information perspective, only the first step in life is difficult. The rest is just a matter of time.

What are the biggest questions in science today: Can we cure cancer, solve the climate crisis, make it to Mars? For Nobel laureate Jack Szostak, the biggest question is still much more fundamental: What is the origin of life?

NEIL deGRASSE TYSON (Astrophysicist): A hellish, fiery wasteland,a molten planet hostile to life, yet somehow, amazingly, this is where we gotour start. How? How did the universe, our planet, how did we ourselves come tobe? How did the first sparks of life take hold here? Are we alone in thecosmos? Where did all the stars and galaxies come from? These questions are asancient as human curiosity itself. And on Origins, a four-part NOVAmini-series, we'll hunt for the answers. This search takes unexpected twistsand turns. Imagine meteors delivering Earth's oceans from outer space. Descendinto a toxic underworld where bizarre creatures hold clues to how life got itsstart. And picture the view when the newborn moon, 200,000 miles closer toEarth than today, loomed large in the night sky. This cosmic quest takes usback in time to within moments of the Big Bang itself and retraces the eventsthat created us, this place we call home and perhaps life elsewhere in thecosmos. Coming up tonight: the origins of life. 041b061a72

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