
DNA Can Survive Reentry from Space - softdev12
http://www.scientificamerican.com/article/dna-can-survive-reentry-from-space/
======
achille
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
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
RNA is highly unstable.

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dthal
_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
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
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_protectio...](http://en.wikipedia.org/wiki/Space_Shuttle_thermal_protection_system)

(Edit: added bit about eutectic)

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ochoseis
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_Spac...](http://en.wikipedia.org/wiki/The_Immortals_%28Cosmos:_A_Spacetime_Odyssey%29)

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
That's fine and dandy, but it doesn't solve how the first lifeform sparked
into existence.

~~~
davyjones
Miller Urey expt.

[http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment#...](http://en.wikipedia.org/wiki/Miller%E2%80%93Urey_experiment#Other_experiments)

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api
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-t...](http://www.technologyreview.com/view/513781/moores-law-and-the-
origin-of-life/)

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?

~~~
alevskaya
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.

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fosk
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
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)

~~~
alanh
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
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
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) ~ &epsilon; 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.

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Roboprog
Good, now let's rebuild Cmdr. Shepard

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alanh
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
I guess you are being downvoted, because the fact "DNA can survive (re?)entry
from space" is not a _proof_.

~~~
kenrikm
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
"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
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"

