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I could have sworn that there was a question that covered this, but I suppose I'm misremembering. If anyone finds one, let me know.

Back in the early days of the Solar System, things were pretty bad. There were many collisions, which made it hard for any particular object to stay the way it was for extended periods of time. In this circumstellar disk, conditions were not good for life.

Perhaps I shouldn't judge, though. Life is pretty tenacious, and it can survive in some of the harshest of places.

So, could life form and survive for an extended period of time (on the order of at least several million years) in a circumstellar disk?

See also, by the way, Could life form in outer space?.

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HDE 226868
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    I answered this question recently with a solution similar to what you're looking at, but I don't think that the feasibility has been explored in a [tag:hard-science] fashion. – Samuel Aug 18 '15 at 16:28
  • @Samuel A gas torus would have different problems; circumstellar disks would have more rocky materials, meaning different interactions between objects inside it. – HDE 226868 Aug 18 '15 at 16:31
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    I'm going to say right now that it's going to be hard to find any liquid water, which I'd consider to be a pretty big problem when trying to create life. Other than that, though, I am very much out of my element on this question. – DaaaahWhoosh Aug 18 '15 at 17:26
  • Then unless your definition for life is Star Trek cannon, and permits sand as one, the I would think the calculations would be more absurd than those for the likely hood of evolution. – DeveloperWeeks Aug 25 '15 at 21:15
  • You mean on proto planets on the disk I take it - rather than microbes surviving in space? – Tim B Aug 27 '15 at 14:09
  • @TimB Yes, on the protoplanets/planetesimals. – HDE 226868 Aug 27 '15 at 15:16
  • Due to the fact that the origin of life on Earth is still one of the great mystery of science, I really don't see how to answer that question in a correct and decent way. Some theories are based on the fact that Life came on Earth riding Asteroids. If that were true, then life could "appear" and somehow survive in your protoplanetary disk. But that's probably as good as you could get. – clem steredenn Sep 01 '15 at 20:23
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    See Larry Nivin’s Smoke Ring. – JDługosz Apr 08 '17 at 18:00

1 Answers1

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Maybe

I note that the OP asks for "exist" and "survive", not "form" and "develop". This lowers the barrier of entry to the question considerably. The brief answer for life as we know it is, "No, there's too many essential conditions missing to support life". However, as the universe is a big place and lots of weird things happen, let's see what there is to see when we seed an early star system.

Temperatures

According to this paper in 1998, the temperature of a protoplanetary disk is:

a moderately warm (500–1500 K) inner disk, surrounded by a cool (50–150 K) outer disk.

Assuming a continuous gradient between the two temperature extremes, there is a zone where liquid water can form and organic molecules don't automatically denature. (I'm probably using the wrong words here but chemistry isn't my strong suit.)

Available Fuel/Food

Recent studies have indicated that organic molecules can form in the protoplanetary disk so there's a decent chance for food and building materials to be nearby.

"Living" Strategies

Dormant Survive - If life is dormant and survives for a few million years then it just got lucky that it didn't fall onto a planet or the sun or get cooked by the protoplanetary disk's heat. Impressive survivability by Earth's standards but not amazing.

Active Survive - If this Life is alive and not in a dormant state then it has solved a number of significant challenges that preclude typical terrestrial life from forming. A long list of these challenges can be found in this answer.

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