Complex extraterrestrial life & chemical elements

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ekeller65

Registered Senior Member
Chemical elements Hydrogen, Helium, Oxygen & Carbon are the most abundant in the universe. In human body Oxygen ,Carbon & Hydrogen are most abundant.

Based on this, is it correct to assume that most of the extraterrestrial complex life ( if exist in multiple planets) are cabon based life with H2O as the main substance ?
 
Pretty much. Silicon is often proposed as an alternative to CHONS based life but it's pretty hard to imagine, as Si is just less reactive, It might seem a little boring or unimaginative to suggest that other life might also be CHONS, but hey, maybe they use ammonia as a solvent instead of water, or something.
 
ekeller65 said:
Chemical elements Hydrogen, Helium, Oxygen & Carbon are the most abundant in the universe. In human body Oxygen ,Carbon & Hydrogen are most abundant.

Based on this, is it correct to assume that most of the extraterrestrial complex life ( if exist in multiple planets) are cabon based life with H2O as the main substance ?
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based on our extremely narrow knowledge of universe...yes it is good to assume that life is just like our own. But reality is way different.
 
draqon said:
based on our extremely narrow knowledge of universe...yes it is good to assume that life is just like our own. But reality is way different.
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The creatures themselves might not be anything like us, but if you assume that the laws of physics and chemistry work the same everywhere (which is probably a pretty safe bet) then it does indeed seem pretty likely that any aliens out there probably have biochemistry based on C, H, N, and O. It's hypothetically possible that there could be alien life based on radically different elements, but if it exists at all it's probably a lot less common.
 
If we want exciting possibilities, consider the effects of a denser or thinner atmosphere, or a higher/lower gravity on the physiologies of the creatures, or indeed the way the entire ecosystem would work.
 
Nasor said:
...then it does indeed seem pretty likely that any aliens out there probably have biochemistry based on C, H, N, and O. It's hypothetically possible that there could be alien life based on radically different elements, but if it exists at all it's probably a lot less common.
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Agreed.
 
Nasor said:
The creatures themselves might not be anything like us, but if you assume that the laws of physics and chemistry work the same everywhere (which is probably a pretty safe bet) . . . .
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For as far as we can see in every direction, which I think is something like twelve billion light years, a good fraction of the universe, the four fundamental forces are universal and unvarying. All of our science is based upon that premise so you could call it the most canonical scientific theory of all.
. . . . then it does indeed seem pretty likely that any aliens out there probably have biochemistry based on C, H, N, and O. It's hypothetically possible that there could be alien life based on radically different elements, but if it exists at all it's probably a lot less common.
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If we encounter a biosphere that is older than ours, we might find artificial life that was created by its more advanced organic creatures. In fact the organic life might be extinct. In one of my favorite novels by one of my favorite authors, James P. Hogan dealt with that scenario in Code of the Lifemaker. Humans find a planet inhabited entirely by self-replicating electromechanical creatures, some of whom have achieved sentience. Since they had begun building machinery based on the CHONS paradigm, they assumed that they were the natural creatures and we were the leftover artifacts. Interesting standoff.
 
Wikipedia says that the ten most common elements in our galaxy, by mass, are:
  • Hydrogen 73.9%
  • Helium 24.0%
  • Oxygen 1.04%
  • Carbon .46%
  • Neon .13%
  • Iron .11%
  • Nitrogen .10%
  • Silicon .06%
  • Magnesium .06%
  • Sulfur .04%
  • All others .1%
 
Fraggle Rocker said:
Wikipedia says that the ten most common elements in our galaxy, by mass, are:
  • Hydrogen 73.9%
  • Helium 24.0%
  • Oxygen 1.04%
  • Carbon .46%
  • Neon .13%
  • Iron .11%
  • Nitrogen .10%
  • Silicon .06%
  • Magnesium .06%
  • Sulfur .04%
  • All others .1%
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Very interesting figures...I trust these reading are merely approximates and generated purely by assumption for imaginative minds!
 
Creeping Death said:
Very interesting figures...I trust these reading are merely approximates and generated purely by assumption for imaginative minds!
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I believe these are generated by spectroscopic analysis of the composition of stars, with the assumption that the cold interstellar gases (which can be significant clouds of gas) have similar composition.
 
Walter L. Wagner said:
I believe these are generated by spectroscopic analysis of the composition of stars, with the assumption that the cold interstellar gases (which can be significant clouds of gas) have similar composition.
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Also spectroscopic analysis of the cold interstellar gases, using background stars as light sources. The observed results all fit nicely with what's mathematically predicted based on what we know about nuclear physics.
 
Isn't the radial velocity of a star that dilates the spectrum result in shift scales with wavelength? As in the case when observing bulge stars in the Milkyway, due to the large and variable visual extinction in the line-of-sight towards the bulge, an analysis in the near-IR is preferred.
 
Creeping Death said:
Isn't the radial velocity of a star that dilates the spectrum result in shift scales with wavelength? As in the case when observing bulge stars in the Milkyway, due to the large and variable visual extinction in the line-of-sight towards the bulge, an analysis in the near-IR is preferred.
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Various things change the emission spectrum of stars, but there are many characteristic emission lines for each star that makes it relatively easy to calibrate where the peaks actually are.
 
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