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Waspie_Dwarf

Comets could have seeded life on Earth

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Evidence that comets could have seeded life on Earth

BERKELEY — It’s among the most ancient of questions: What are the origins of life on Earth?

A new experiment simulating conditions in deep space reveals that the complex building blocks of life could have been created on icy interplanetary dust and then carried to Earth, jump-starting life.

Chemists from the University of California, Berkeley, and the University of Hawaii, Manoa, showed that conditions in space are capable of creating complex dipeptides – linked pairs of amino acids – that are essential building blocks shared by all living things. The discovery opens the door to the possibility that these molecules were brought to Earth aboard a comet or possibly meteorites, catalyzing the formation of proteins (polypeptides), enzymes and even more complex molecules, such as sugars, that are necessary for life.

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This seems an unnecessary complication; not an unreasonable one, but unnecessary. We understand that the same chemicals can be formed on the earth, so why hypothesize external sources?

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This seems an unnecessary complication; not an unreasonable one, but unnecessary. We understand that the same chemicals can be formed on the earth, so why hypothesize external sources?

We do know that the same chemicals can form on Earth, however why ignore a possibility? Science isn't about humans deciding what is and what isn't necessary (the universe decides that), it is about determining what is true.

Amino acids can be formed on comets. Early in Earth's history comet frequently collided with the Earth. Life occurred on Earth very quickly after the crust solidified. Is it a huge stretch of the imagination to link these events?

The question is an important one. If the ingredients of life arose on Earth then they would have to arise independently on other planets and moons in the solar system. If, on the other hand, those ingredients were seeded from comets then they will have been seeded right across the solar system. If the second option is correct then it is far more likely that we will find life on Mars, Europa and other worlds in the solar system.

Comets are likely to exist in other (maybe all) solar systems. If life is brought to planets via comets them primitive life is likely to be very common.

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The point about comets seeding planets that can't develop their own organic-precursor molecules is one I hadn't thought of, although I don'[t know that such planets would be able to go onward and develop life either.

The point that primitive life -- I take it basically single celled organisms -- is likely common seems correct regardless, considering how quickly such life appeared on the earth.

Be all this as it may be, comets are worth detailed study on their own.

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The point that primitive life -- I take it basically single celled organisms -- is likely common seems correct regardless, considering how quickly such life appeared on the earth.

Maybe, but that would depend on WHY it developed so quickly on Earth, you can't extrapolate from a single data point. We simply don't know yet how rare those conditions were. If it turns out that the chemicals for life are raining down from the sky on pretty much every planet in the universe then we can say with a high degree of certainty, that the conditions that lead to life on Earth or not unique or even rare, but the norm.

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I buy all that. It's just that even if DNA molecules were raining down, life isn't going to happen if the ground is hostile.

I've always had a picture of an early earth (after the pyrotechnics settled down) mostly covered with a warmish ocean in a reducing atmosphere (so big molecules don't get oxidized) with volcanoes and lightning and ocean vents and so on providing energy building a sort-of global soup, stewing for millions or even a billion years, where here and there self-replicating molecules are basically inevitable, and, in a few places where UV protection exists, life.

That we would ever be able to work out in detail the steps of all this has seemed to me extremely unlikely. There may be gazillions of paths the process could take.

I suppose adding comets raining down amino acids and the like just makes it that much more certain.

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This experiment certainly seems to support the idea that the formation of life throughout space could be very common. The greater the number of world with primitive life, the better the odds of at least the occasional development of more complex life. Good news, it seems to me. A populated universe should be far more interesting than a lonely one.

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I buy all that. It's just that even if DNA molecules were raining down, life isn't going to happen if the ground is hostile.

Agreed, but even within our solar system you have Mars, Europa, Ganymede and maybe some of the other outer planet satellites were conditions may be far from hostile. With at least four chances of life occurring in just this solar system then it seems likely that simple life has/will occur throughout the universe.

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