5 ms·

DNA Can Survive Reentry from Space

73 points by softdev12 12y ago

Roboprog 12y ago
Good, now let's rebuild Cmdr. Shepard
alanh 12y ago
Proof we possibly originated from extraterrestrial life! edit oh, grow up, downvoters. panspermia is a real concept http://www.livescience.com/13363-7-theories-origin-life.html http://www.livescience.com/13363-7-theories-origin-life.html
- throwaway7808 12y ago
  I guess you are being downvoted, because the fact "DNA can survive (re?)entry from space" is not a proof.
  - kenrikm 12y ago
    I think "Proof (that we) Possibly" kinda sums it up. This is "Proof" that there is a possibility (does not rule it out). He's being down voted because people are splitting hairs about the wording. What he said was generally correct however the word "proof" has a strong pull in one direction.
    - mikeash 12y ago
      "Proof we possibly" is an oxymoron, like "60% of the time it works every time." It's not so much splitting hairs as it is attempting vainly to understand phrasing that inherently makes no sense.
      - kenrikm 12y ago
        I agree it was bad phrasing, that was not my point. I was simply pointing out that even though his wording was bad what he was trying to get across (Proof that is's still a viable hypothesis) was technically correct. Here i'll fix it for you "This is proof that that DNA can survive re-entry from space, due to this finding there is still a possibility that life came from somewhere else"
      - alanh 12y ago
        Harsh! Yes, it’s an oxymoron. It doesn’t “make no sense;” it was an attempt at humor (which clearly failed).
fosk 12y ago
This could make more plausible the theory that life on Earth is coming from space and then it evolved from there, rather than being born from scratch on Earth.
- 3rd3 12y ago
  By Occams Razor, however, it’s probably better to assume that it formed spontaneously on Earth: "Just turning on the spark in a basic pre-biotic experiment will yield 11 out of 20 amino acids." [1] [1]: https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment
  - thret 12y ago
    This is conjecture. We don't really know how many billions of years it takes to spontaneously evolve life. Panspermia may well be a much simpler vector.
  - alanh 12y ago
    Hmm, I wonder if Occam's razor is really applicable. Is it simpler for life to form on multiple planets, or one and spread? I would guess your interpretation is more likely, but I suppose we don't know
    - 3rd3 12y ago
      It’s applicable if one hypothesis is simpler than the other. Panspermia simply defers the origin of life elsewhere and now you have to explain how seeds survived travelling through the hostile environment of space and impacting on Earth, which complicates it quite a bit.
      - tjradcliffe 12y ago
        Ockham's razor is either useless, or a special case of Bayes' Rule. People argue endlessly about it because they fail to recognize they are assuming different priors. If the Urey experiment is reasonably representative of conditions on primordial Earth, no further work is required to get amino acids. So for some people P(terrestrial primordial amino acids) is ~1 If the Murchison meteor and other evidence is correct, amino acids are common in the universe. Data from the Philae lander may tell us more about this. So for some people P(extra-terrestrial primordial amino acids) is ~1 Nor are these exclusive groups. It appears amino acids aren't all that hard to make, so they may have both fallen from the sky and been created on Earth. But... amino acids are not life. There is a further step that is required for the actual pan-spermia hypothesis: the synthesis of more complex molecules, like RNA and DNA. If you think P(RNA|amino acids) ~ 1 then pan-spermia becomes at best irrelevant: not impossible, but not very interesting. If you think P(R/DNA|amino acids) ~ ε then pan-spermia becomes very important, because it is far more likely than not that life on Earth is due to RNA or DNA that descend from an original synthesis that happened elsewhere. Evidence suggests RNA synthesis given amino acids is not very probable. I don't believe it has ever been observed to happen spontaneously the way amino acids are spontaneously synthesized in the Urey experiment. So pan-spermia cannot be dismissed on the basis that it is uninteresting. DNA propogating itself across the universe is also not very probable, so the two hypotheses remain in competition, and it isn't obvious which is more plausible. Pan-spermia requires things like "DNA can survive re-entry." So the OP is correct: discovering that DNA can survive re-entry makes "Life originated elsewhere" more plausible. You'll notice I never used the word "simplicity" in any of this. There is no simplicity: only probability and plausibility. Evidence is more or less probable. Propositions are more or less plausible. Bayes' rule is the only way to update our beliefs consistently, such that no matter what order we get the evidence we come to the conclusion.
deleted 12y ago
[deleted]
api 12y ago
I've wondered this for many years: could the idea that life originated here on Earth be the final geocentrism? This is really quite interesting too: http://www.technologyreview.com/view/513781/moores-law-and-the-origin-of-life/ http://www.technologyreview.com/view/513781/moores-law-and-t... All this is pure hypothesis and speculation until we can find some life out there and engage in some comparative analysis. If we found life elsewhere and it appeared to trace back to a common ancestor, then this would suggest that life originated far back in the history of the cosmos rather than independently in many places. Perhaps life -- if interpreted as a phase of matter -- arose along with all the other phases of matter during the early cooling of the universe?
- throwaway7808 12y ago
  "The final geocentricism.". Duh. You could be in a mixed state of |life had originated on earth| + |life had originated elsewhere| + |physics doesn't actually exists, and you are just a bitstring|. edit: downvoter ;) you are an unfriendly and uneducated bitstring ;)
- alevskaya 12y ago
  The problem with life evolving this early is that life absolutely requires the higher-mass elements from the supernovae arising from the first few stellar generations. The early universe was an inhospitable desert of Hydrogen.
achille 12y ago
Just note that DNA itself is code and completely useless without an interpreter/compiler. The DNA is just a storage mechanism, the true complexity relies on the cell. See: http://ds9a.nl/amazing-dna/ http://ds9a.nl/amazing-dna/ If we lost all cells but had DNA, we could not do anything with it. The same way that source code is useless if you don't have a compiler.
- SapphireSun 12y ago
  Too bad they didn't test RNA... self replicating RNA doesn't need a compiler. ;) https://en.wikipedia.org/wiki/Viroid https://en.wikipedia.org/wiki/Viroid (possible relics from the theoretical RNA world still around today)
  - lambdaphage 12y ago
    RNA is highly unstable.
ochoseis 12y ago
The recent Cosmos remake has a good episode that touches on this. I think it's http://en.wikipedia.org/wiki/The_Immortals_%28Cosmos:_A_Spacetime_Odyssey%29 http://en.wikipedia.org/wiki/The_Immortals_%28Cosmos:_A_Spac... One theory set forth is that earlier in Earth's history, while bacteria were first evolving meteors would periodically strike and extinguish life, but cast rocks with dormant bacteria into space that would later re-enter and re-seed the planet after the dust settled. First time I heard the idea but it's intriguing, and segues into the whole idea of panspermia.
- kiba 12y ago
  That's fine and dandy, but it doesn't solve how the first lifeform sparked into existence.
  - ende 12y ago
    Very gradually.
  - kingkawn 12y ago
    RNA can autonomously assemble with the right mix of raw materials and minerals.
  - davyjones 12y ago
    Miller Urey expt. http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment#Other_experiments http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment#...
dthal 12y ago
Temperatures on the exterior of the rocket reached as high as 115.4 degrees Celsius during liftoff and 128.3 degrees Celsius during atmospheric reentry Doesn't that re-entry temperature seem way too low? I get that its probably a rear-facing surface, but still...
- userbinator 12y ago
  Yes, it's extremely low - even a "rear-facing surface" would get hot enough to melt metals such as aluminium during a typical reentry. That's why the space shuttle has all those insulating tiles.
  - TheSpiceIsLife 12y ago
    Maybe not? Aluminium melts at 660.32 °C / 1220.58 °F [1]. I guess aluminium alloys probably melt at slightly higher temperatures. Unless, of course, there's an aluminium alloy eutectic - I don't know. "Felt reusable surface insulation (FRSI). White Nomex felt blankets on the upper payload bay doors, portions of the midfuselage and aft fuselage sides, portions of the upper wing surface and a portion of the OMS/RCS pods. Used where temperatures stayed below 371 °C (700 °F)."[2] "The Space Shuttle thermal protection system (TPS) is the barrier that protected the Space Shuttle Orbiter during the searing 1,650 °C (3,000 °F) heat of atmospheric reentry."[2] 1. http://en.wikipedia.org/wiki/Aluminium http://en.wikipedia.org/wiki/Aluminium 2. http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protectio... (Edit: added bit about eutectic)
- rflrob 12y ago
  The rockets used were sounding rockets—not orbital. I'm not sure just how much slower they are than orbital rockets, but if my hours of playing KSP are any guide, the answer is "quite a bit slower".

73 points by softdev12 12y ago

Good, now let's rebuild Cmdr. Shepard

alanh 12y ago

Proof we possibly originated from extraterrestrial life! edit oh, grow up, downvoters. panspermia is a real concept http://www.livescience.com/13363-7-theories-origin-life.html http://www.livescience.com/13363-7-theories-origin-life.html

throwaway7808 12y ago
I guess you are being downvoted, because the fact "DNA can survive (re?)entry from space" is not a proof.
- kenrikm 12y ago
  I think "Proof (that we) Possibly" kinda sums it up. This is "Proof" that there is a possibility (does not rule it out). He's being down voted because people are splitting hairs about the wording. What he said was generally correct however the word "proof" has a strong pull in one direction.
  - mikeash 12y ago
    "Proof we possibly" is an oxymoron, like "60% of the time it works every time." It's not so much splitting hairs as it is attempting vainly to understand phrasing that inherently makes no sense.
    - kenrikm 12y ago
      I agree it was bad phrasing, that was not my point. I was simply pointing out that even though his wording was bad what he was trying to get across (Proof that is's still a viable hypothesis) was technically correct. Here i'll fix it for you "This is proof that that DNA can survive re-entry from space, due to this finding there is still a possibility that life came from somewhere else"
    - alanh 12y ago
      Harsh! Yes, it’s an oxymoron. It doesn’t “make no sense;” it was an attempt at humor (which clearly failed).

fosk 12y ago

This could make more plausible the theory that life on Earth is coming from space and then it evolved from there, rather than being born from scratch on Earth.

3rd3 12y ago
By Occams Razor, however, it’s probably better to assume that it formed spontaneously on Earth: "Just turning on the spark in a basic pre-biotic experiment will yield 11 out of 20 amino acids." [1] [1]: https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment https://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment
- thret 12y ago
  This is conjecture. We don't really know how many billions of years it takes to spontaneously evolve life. Panspermia may well be a much simpler vector.
- alanh 12y ago
  Hmm, I wonder if Occam's razor is really applicable. Is it simpler for life to form on multiple planets, or one and spread? I would guess your interpretation is more likely, but I suppose we don't know
  - 3rd3 12y ago
    It’s applicable if one hypothesis is simpler than the other. Panspermia simply defers the origin of life elsewhere and now you have to explain how seeds survived travelling through the hostile environment of space and impacting on Earth, which complicates it quite a bit.
    - tjradcliffe 12y ago
      Ockham's razor is either useless, or a special case of Bayes' Rule. People argue endlessly about it because they fail to recognize they are assuming different priors. If the Urey experiment is reasonably representative of conditions on primordial Earth, no further work is required to get amino acids. So for some people P(terrestrial primordial amino acids) is ~1 If the Murchison meteor and other evidence is correct, amino acids are common in the universe. Data from the Philae lander may tell us more about this. So for some people P(extra-terrestrial primordial amino acids) is ~1 Nor are these exclusive groups. It appears amino acids aren't all that hard to make, so they may have both fallen from the sky and been created on Earth. But... amino acids are not life. There is a further step that is required for the actual pan-spermia hypothesis: the synthesis of more complex molecules, like RNA and DNA. If you think P(RNA|amino acids) ~ 1 then pan-spermia becomes at best irrelevant: not impossible, but not very interesting. If you think P(R/DNA|amino acids) ~ ε then pan-spermia becomes very important, because it is far more likely than not that life on Earth is due to RNA or DNA that descend from an original synthesis that happened elsewhere. Evidence suggests RNA synthesis given amino acids is not very probable. I don't believe it has ever been observed to happen spontaneously the way amino acids are spontaneously synthesized in the Urey experiment. So pan-spermia cannot be dismissed on the basis that it is uninteresting. DNA propogating itself across the universe is also not very probable, so the two hypotheses remain in competition, and it isn't obvious which is more plausible. Pan-spermia requires things like "DNA can survive re-entry." So the OP is correct: discovering that DNA can survive re-entry makes "Life originated elsewhere" more plausible. You'll notice I never used the word "simplicity" in any of this. There is no simplicity: only probability and plausibility. Evidence is more or less probable. Propositions are more or less plausible. Bayes' rule is the only way to update our beliefs consistently, such that no matter what order we get the evidence we come to the conclusion.

deleted 12y ago

[deleted]

api 12y ago

I've wondered this for many years: could the idea that life originated here on Earth be the final geocentrism? This is really quite interesting too: http://www.technologyreview.com/view/513781/moores-law-and-the-origin-of-life/ http://www.technologyreview.com/view/513781/moores-law-and-t... All this is pure hypothesis and speculation until we can find some life out there and engage in some comparative analysis. If we found life elsewhere and it appeared to trace back to a common ancestor, then this would suggest that life originated far back in the history of the cosmos rather than independently in many places. Perhaps life -- if interpreted as a phase of matter -- arose along with all the other phases of matter during the early cooling of the universe?

throwaway7808 12y ago
"The final geocentricism.". Duh. You could be in a mixed state of |life had originated on earth| + |life had originated elsewhere| + |physics doesn't actually exists, and you are just a bitstring|. edit: downvoter ;) you are an unfriendly and uneducated bitstring ;)
alevskaya 12y ago
The problem with life evolving this early is that life absolutely requires the higher-mass elements from the supernovae arising from the first few stellar generations. The early universe was an inhospitable desert of Hydrogen.

achille 12y ago

Just note that DNA itself is code and completely useless without an interpreter/compiler. The DNA is just a storage mechanism, the true complexity relies on the cell. See: http://ds9a.nl/amazing-dna/ http://ds9a.nl/amazing-dna/ If we lost all cells but had DNA, we could not do anything with it. The same way that source code is useless if you don't have a compiler.

SapphireSun 12y ago
Too bad they didn't test RNA... self replicating RNA doesn't need a compiler. ;) https://en.wikipedia.org/wiki/Viroid https://en.wikipedia.org/wiki/Viroid (possible relics from the theoretical RNA world still around today)
- lambdaphage 12y ago
  RNA is highly unstable.

ochoseis 12y ago

The recent Cosmos remake has a good episode that touches on this. I think it's http://en.wikipedia.org/wiki/The_Immortals_%28Cosmos:_A_Spacetime_Odyssey%29 http://en.wikipedia.org/wiki/The_Immortals_%28Cosmos:_A_Spac... One theory set forth is that earlier in Earth's history, while bacteria were first evolving meteors would periodically strike and extinguish life, but cast rocks with dormant bacteria into space that would later re-enter and re-seed the planet after the dust settled. First time I heard the idea but it's intriguing, and segues into the whole idea of panspermia.

kiba 12y ago
That's fine and dandy, but it doesn't solve how the first lifeform sparked into existence.
- ende 12y ago
  Very gradually.
- kingkawn 12y ago
  RNA can autonomously assemble with the right mix of raw materials and minerals.
- davyjones 12y ago
  Miller Urey expt. http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment#Other_experiments http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment#...

dthal 12y ago

Temperatures on the exterior of the rocket reached as high as 115.4 degrees Celsius during liftoff and 128.3 degrees Celsius during atmospheric reentry Doesn't that re-entry temperature seem way too low? I get that its probably a rear-facing surface, but still...

userbinator 12y ago
Yes, it's extremely low - even a "rear-facing surface" would get hot enough to melt metals such as aluminium during a typical reentry. That's why the space shuttle has all those insulating tiles.
- TheSpiceIsLife 12y ago
  Maybe not? Aluminium melts at 660.32 °C / 1220.58 °F [1]. I guess aluminium alloys probably melt at slightly higher temperatures. Unless, of course, there's an aluminium alloy eutectic - I don't know. "Felt reusable surface insulation (FRSI). White Nomex felt blankets on the upper payload bay doors, portions of the midfuselage and aft fuselage sides, portions of the upper wing surface and a portion of the OMS/RCS pods. Used where temperatures stayed below 371 °C (700 °F)."[2] "The Space Shuttle thermal protection system (TPS) is the barrier that protected the Space Shuttle Orbiter during the searing 1,650 °C (3,000 °F) heat of atmospheric reentry."[2] 1. http://en.wikipedia.org/wiki/Aluminium http://en.wikipedia.org/wiki/Aluminium 2. http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protectio... (Edit: added bit about eutectic)
rflrob 12y ago
The rockets used were sounding rockets—not orbital. I'm not sure just how much slower they are than orbital rockets, but if my hours of playing KSP are any guide, the answer is "quite a bit slower".