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Today in science from wired.

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If you like this podcast,

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can we recommend another one It's called

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Big Picture Science. You can hear it

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wherever you get your podcast and its

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name tells part of the story. The

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Big picture questions and the most

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interesting research in science.

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Seth and I are the host. Seth is a

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scientist. I am Molly and I'm a science journalist

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and we talk to people smarter

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than us and we have fun along the way. The

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show is called Big Picture Science, NSF

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said, you can hear it wherever you get your podcast.

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Did the seeds of life ride to Earth

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inside an asteroid? Biological

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amino acids could have celestial or

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terrestrial roots. An experiment

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simulated their formation in deep space

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but the mystery isn't solved yet

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by Katrina Miller. Billions

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of years ago, our solar system coalesced

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within an interstellar a molecular cloud.

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A nursery made up of gas and dust

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that clumped together to form stars,

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asteroids, and planets. Eventually,

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our own earth. Somewhere along

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that cosmic timeline, the amino acids

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that preceded life appeared. These

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molecules chained together to form the

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protein responsible for nearly every

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biological function. But where

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those amino acids come from has

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been an enduring mystery. Did

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these biological building blocks somehow

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arise from the pre biotic conditions of

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early earth? Or was our planet

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seeded with these ingredients from elsewhere

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in the universe. Some

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astronomers think life's heritage must

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have begun off planet because amino

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acids have been discovered in meteorites,

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celestial time capsules composed

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of the same primitive materials from which

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our solar system formed. meteorite

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as a fragment of an asteroid or any

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other space rock that has fallen to

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earth. But despite their best

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efforts, scientists can't pin down

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exactly how these molecules got there.

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Experiments in lab can't reproduce what's

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found in nature. A team

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of researchers at NASA's Cosmic

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Ice Laboratory set out to investigate

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this discrepancy by simulating the

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chemical activities of interstellar molecular

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clouds and asteroids, to places

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known to form amino acids. While

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they didn't solve the mystery, The results

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they published in early January hint

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that something complicated is happening

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to produce the distribution of materials found

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in meteorites. Knowing

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where these amino acids come from could

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say something about the possibility of life

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elsewhere in the cosmos says Donna

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Kusum, an astrochemist at Southwest

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Research Institute who led the study.

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If they came from asteroids in our own

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solar system, It might mean these ingredients

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are unique to our region of the universe.

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But if they were birthed by our parent molecular

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cloud, Gossam says that tells

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us this cloud essentially has a frozen

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starter kit of life that's been distributed

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to other solar systems and potentially

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other planets. Amino

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acids are easy enough to create. Past

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studies have shown that under the right conditions,

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they arise when cosmic rays irradiate

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interstellar ice. And from the chemistry

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turning inside the bellies of asteroids. Short

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chains of amino acids can even spontaneously

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form on star dust. But

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other experiments prove that these molecules

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could have once been generated on our

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planet inside ancient deep

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sea hydrothermal vents. Or

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when lightning struck the organic molecular

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soup of early earth. Yet

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these molecules by themselves and even

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the proteins they form, are not

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life. Any more than a silicon wafer

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alone is a computer, says study

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coauthor, Jason Wirtgen, an astrobiologist

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at NASA Goddard Space Flight Center,

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That wafer is necessary if organized

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in a particular way, connected to a power

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supply and encoded with software

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that permits it to do something, he says.

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Similarly, the true seeds of life

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must be able to carry out characteristic functions

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like making energy, replicating and

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passing down traits to offspring. Nailing

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down the source of prebiotic amino

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acids then is the first step toward uncovering

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the processes that trigger biology. Still,

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it's been hard to figure out which of these pathways

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start us or primordial soup under

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sea events or irradiated space ice

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lead to life. Getting amino

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acids is relatively straightforward since

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working, but getting the amino acids

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used in biology is more of a mystery.

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Nearly a hundred different types of amino

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acids have been observed in meteorites, but

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only a dozen of the twenty that are essential

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for life have been found. Biological

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amino acids also have a peculiarity

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that gives them away. They all have

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a left handed structure, whereas a

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biotic processes create left and

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right handed molecules in equal measure.

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Several meteorites discovered on Earth

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have an excess of left handed amino acids

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to Orkin says, the only nonbiological

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system ever observed with this imbalance.

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For this experiment, the team tested the

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theory that amino acids were first created

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within interstellar molecular clouds,

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then rode to Earth inside asteroids.

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They decided to recreate the conditions these

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molecules would have been exposed to at each

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stage in their journey. If this

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process produced the same assortment of amino

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acid in the same ratios as those

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found in recovered meteorites, it

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would help validate the theory. The

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researchers began by creating the most common

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molecular ices found in interstellar

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clouds, water, carbon dioxide,

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methanol, and ammonia in a vacuum

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chamber. Then they bombarded the

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ices with a beam of high energy

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protons mimicking collisions with

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cosmic rays in deep space. The

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ices broke apart and reassembled into

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larger molecules, eventually forming

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a gunky residue visible to the naked

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eye, chunks of amino acids.

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Next, they simulated the interior of

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asteroids, which contain liquid water

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and can be surprisingly hot, between

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fifty and three hundred degrees Celsius. They

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submerged the residue in water at fifty

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and one hundred twenty five degrees Celsius for

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different lengths of time. This

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boosted the levels of some amino acids,

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but not others. The amount of glycine

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and serine for example both doubled.

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The alanine content stayed the same.

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But their relative levels remained consistent

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before and after the chunks were plunged

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into the asteroid simulation. There

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was always more glycine than serine

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and more serine than alanine. This

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trend is noteworthy, Kasimov says,

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because it shows that conditions within interstellar

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cloud would have had a strong influence on

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the makeup of amino acids inside the asteroid.

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But ultimately, their experiment ran into

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the same problem other lab studies have.

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The distribution of amino acids still

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didn't match that found in real meteorites.

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The most notable difference was the excess

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of beta alanine and alpha alanine in

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their lab samples. In meteorites,

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this typically occurs the other way around.

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If there was a recipe for creating life's precursors,

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they hadn't found it. That's likely

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because their recipe was too simple, custom

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sess. The next experiments need

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to be more complicated. We need to add

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more minerals and consider more relevant

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asteroid parameters and conditions. But

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there's another possibility. Maybe

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the meteoric samples they've been using

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for comparison are contaminated, As

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the meteorites crash landed, they

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could have been changed by their interactions with

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Earth's atmosphere and biology. As

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well as centuries of geological activity

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that had melted, subducted and recycled

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the planetary surface. One

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way to test this is by using a pristine

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sample as the starting point. This

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September, NASA's Osiris Rex mission

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will bring home something like a two hundred

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gram chunk of the asteroid Bennu. That's

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forty times bigger than the last sample

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we got of untouched space rock.

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A quarter of the sample will be analyzed for

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amino acids which will help nail down the

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source of discrepancies between lab studies

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and meteorites. It could also

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uncover what other fragile materials are

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present in asteroids, but can't survive

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the trip to our planet without the protection of

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a spacecraft. That information

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would help Kossum's team perfect the recipe.

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The rest of the Benoeu sample, like those

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from the Apollo mission fifty years ago,

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will be tucked away in airtight containers

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to give not yet born scientists a chance

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to analyze the asteroid with not yet invented

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techniques and technologies. This

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is the legacy of sample returns says

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to work in who is a project scientist

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for Osiris Rex. Lab experiments

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like these, he says, those simulating the

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conditions of space are critical for

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interpreting these samples. A

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better understanding of asteroid chemistry will

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come in handy when analyzing the retrieved

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space rock and help scientists figure

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out which of their theories best match up with

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nature. There's also a third

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way to think about this issue. Maybe

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we are looking too far from home. Maybe

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the unique conditions that give rise to biology

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happened here, not in space.

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Yana Broomberg, a bioinformatician at

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Rutgers University, thinks the secret to

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life will be found in Earth based biological

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records rather than geological ones.

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Rocks have a tendency to get ground up

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and cycled, she says. It's hard

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to trace history this way. Instead,

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Bromberg looks for the genetic blueprints for

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making cellular energy, a process

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that could have been invented by and inherited

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from ancient proteins created

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from Earth's initial ooze. Last

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year, she published work showing similarities

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in the cores of modern proteins used

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by different organisms. Hinting

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that they may trace back to the same ancestry.

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But while she favors a planetary origin,

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Bromberg doesn't think only Earth could

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give rise to life. My suspicion

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is that you can make amino acids from any

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primordial soup regardless of

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the planet you're on, she says. Maybe

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there is this special unique niche environment

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that only existed in one place and then

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things got spit out. That would be

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cool to know, says planetary scientist, Erin

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Burton, who analyzes astromaterials

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at NASA's Johnson Space Center to understand

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what chemical processes could have led to

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life. His gut tells him that

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biology emerged on earth, but

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that's not the impetus driving his research.

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Wherever we think it started, how did

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it start? That for me is the

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interesting question, and then we'll answer

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where along the way. It's

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possible that the answer to whether life started

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on Earth or in space is both.

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Maybe in Earth's case, space was irrelevant

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except for the delivery of raw materials to

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work and says, and everything important

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subsequently happened here. But it's

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also possible that the same chemical processes

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are also playing out in deep space.

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They do, after all, use the same ingredients.

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That could mean there are many environments

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brimming with potential for life in our universe,

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both on the ground and in the heavens.

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Like what you learned,