If We Find Evidence of Life on Mars Should We Risk Going There?

[BAYLOR]

The Dinosaurs never saw it coming

We likely wouldn't be here if the asteroid hadn't hit . But I do wish some of the non avian dino's like Triceratops could have made it. My favorite dino.

 

[BAYLOR]

Im almost tempted to read Kim stanley Robinson's Mars trilogy, just to see how he imagines mars can be terraformed.

 

[Ray McCarthy]

But I do wish some of the non avian dino's like Triceratops could have made it. My favorite dino.

Not T. Rex?

See http://xkcd.com/1211/
(always hover mouse)

 

[Venusian Broon]

Outside the confines of our safe little Earth, we have a very big and very hostile universe. So many things out there could destroy life on Earth.

Hey man, you seem a bit down with your posts Baylor! <Big manly supportive hug>

Actually I'd say little Earth was one of the most dangerous places for life - look at the number of extinction events that have occurred, maybe more of a Medea rather than a Gaia. Other places outside Earth look like they have been unchanged for billions of years.

However, if it was not for these extinction events and vastly changing conditions we would not be here, so I can't really complain, we gotta have them.

 

[Stephen Palmer]

I got this off the interweb, so it must be true:

It all comes down to thermodynamics.

Specifically, for an element to link to itself in long chains, you need three things:

1. The ability to form more than one bond per atom. This excludes hydrogen and the halogens, for example. We will also exclude the metals, since they don't form localized covalent bonds to themselves and so cannot form chains of atoms.
2. A preference for single bonds over multiple bonds. That is, two single bonds should be more energetically stable than one double bond, and three single bonds than one triple bond.
3. The oxide must not be too much more stable than the pure element. Oxygen is the third most common atom in the universe, and an overwhelming tendency to bond to oxygen will mean that an element will never be found except as the oxide.
4. Finally, the bond to hydrogen must be reasonably strong, compared to the hydrogen-oxygen bond. Hydrogen is the most abundant atom in the universe and (as you indicated in your question) is commonly used to "cap off" chains of atoms. But many compounds of hydrogen are spontaneously flammable in the presence of oxygen!

Single vs. Multiple Bonds
If we confine ourselves to the first-row elements carbon, nitrogen and oxygen, we find the following bond strengths:


Bond type Strength Bond type Strength Bond type Strength
C-C 83 kcal/mol N-N 39 kcal/mol O-O 35 kcal/mol
C=C 146 kcal/mol N=N 100 kcal/mol O=O 119 kcal/mol
CºC 200 kcal/mol NºN 226 kcal/mol
Information in this table is taken from M.A. Fox and J.K. Whitesell, Organic Chemistry, 2nd Ed., Jones & Bartlett, 1997. Values are averages and will differ somewhat depending on the source of data.
Notice that it is favorable for carbon to form singly-bonded chains. For example, two C-C bonds are worth more than one C=C bond: 2 × 83 = 166 > 146.

But nitrogen and oxygen, though formally capable of forming extensive chains of atoms, cannot do so because of the weakness of N-N and O-O single bonds. Quite simply, three N-N bonds are so much weaker than one NºN bond (3 × 39 = 117 << 226) that polyazines (NR)n are explosive! The same is true for peroxides, compounds containing O-O single bonds.

Of course, once you get below the first row multiple bonding becomes much less energetically favorable. Silicon, phosphorus and sulfur can all be found in long, singly-bonded chains or network compounds. The most stable forms of elemental silicon, phosphorus and sulfur (S8) contain polymeric chains or rings of atoms bonded to each other by single bonds. This is also true for boron, arsenic, selenium and tellurium.

 

[Ray McCarthy]

This is why only carbon can be the basis of true organic / Biological processes.
Silicon the next most suitable element, fails, as the oxide is VERY stable and a solid at all reasonable temperatures for organic processes. Oxidised Silicon is basically sand / glass / obsidian / quartz.
There are other reasons why silicon is much less suitable than carbon.

Silicon in the Galaxy or Solar system is VERY much less common than carbon. But Planets with rocky crusts are far more silicon than carbon compounds. If you have silicon, you get rocks. The carbon based life lives on top of them

 

[Dennis E. Taylor]

Going off on a slight tangent, Someone mentioned Saturn Rukh (By Robert Forward) in another post. His isn't the only story with life on a gas giant. I'm just wondering (and I haven't had enough coffee yet to be able to research it ) if all the elements are available in the Jovian atmosphere to build carbon-based life.

 

[Ray McCarthy]

Maybe, and using Ammonia instead of Water?
It's fairly slim.

 

[Mirannan]

Maybe, and using Ammonia instead of Water?
It's fairly slim.

Well, ammonia is a polar solvent rather like water although it has some differences of course. Suitable for temperatures rather lower than those of Earth, and one more thing that makes it possibly viable as a life solvent is that nitrogen is fairly common so there are likely to be places with enough of the stuff.

 

[BAYLOR]

The worst event being Devonian

Not T. Rex?

See http://xkcd.com/1211/
(always hover mouse)

Avian Dino's yes ive read about that one.


I read something else that said that the Dino's were in decline long before the asteroid. The fossils record prior to the extinction even show a decline in the number of species.

 

[BAYLOR]

If we do find evidence of vertebrae life on Mars, that would be a very troubling discovery.

 

[Stephen Palmer]

We won't.

 

[Venusian Broon]

But if we did - why would it be troubling?

 

[BAYLOR]

But if we did - why would it be troubling?

As a stark reminder to us that life on Earth will one day come to an end by something beyond our control , an asteroid hitting us or a passing star which would disrupt earth orbit and probably throw us into space or swallowed by a unseen black hole.

We know that in a billion years the sun will be about 20 percent hotter which will likely scorch the surface clean of life.

 

[Venusian Broon]

As a stark reminder to us that life on Earth will one day come to an end by something beyond our control , an asteroid hitting us or a passing star which would disrupt earth orbit and probably throw us into space or swallowed by a unseen black hole.

We know that in a billion years the sun will be about 20 percent hotter which will likely scorch the surface clean of life.

That's far too morbidly fatalistic on a cosmic scale for me, I'm afraid. I'd rather focus on the bright, optimistic bits during the short duration that my life will give me, but I respect your right to dwell on what might or might not happen a billion years from now .

 

[BAYLOR]

That's far too morbidly fatalistic on a cosmic scale for me, I'm afraid. I'd rather focus on the bright, optimistic bits during the short duration that my life will give me, but I respect your right to dwell on what might or might not happen a billion years from now .

Im given to being slightly pessimistic about the future. My outlook does tend to be cosmic isn scale .

 

[Ray McCarthy]

We won't.

Certainly not alive. A fossil would be intriguing. Especially if the helmet visor or other pieces of the suit survive

 

[BAYLOR]

Certainly not alive. A fossil would be intriguing. Especially if the helmet visor or other pieces of the suit survive

Mars lost it's oceans 3 billion years ago , not enough time for any kind of vertebrae life forms to have evolved.

 

[Dennis E. Taylor]

Mars lost it's oceans 3 billion years ago , not enough time for any kind of vertebrae life forms to have evolved.

Assuming it evolved on Mars...

 

[Stephen Palmer]

We know that in a billion years the sun will be about 20 percent hotter which will likely scorch the surface clean of life.

That happens a bit later on. One billion years from now the big change will be the absence of carbon dioxide in the atmosphere, which halts all photosynthesis. Animal life fades as a consequence. Bacteria etc will be just fine for a long while afterwards.