A second Genesis more likely if life is found on Europa or Enceladus

[pinball1970]

TL;DR Summary

Life on Europa has been discussed on threads on pf previously. This post relates to models (Jay Melosh) looking at whether life on Europa/Enceladus would be the result from lithopanspermia or from scratch, abiogenesis. Some NASA missions in the pipeline may shed some light on this in the next decade with 'Dragonfly' scheduled for 2026.
This is a summary of one or two points from the American geophysical Union from last week.

https://www.space.com/alien-life-europa-enceladus-second-genesis.html

 

[Fred Wright]

From the article,
"We know that about 1 ton of Mars rocks that are fist-size or larger rain down on Earth every year. "
How do we know that? Anyone?

 

[pinball1970]

From the article,
"We know that about 1 ton of Mars rocks that are fist-size or larger rain down on Earth every year. "
How do we know that? Anyone?

There a few papers outlining the mechanism and evidence.
https://arxiv.org/abs/1311.2558
This from NASA
https://mars.jpl.nasa.gov/news/nasa-rover-confirms-mars-origin-of-some-meteorites/

 

[BillTre]

It also seems to me to be unlikely that life would get around easily among planets, but you never can tell.
Life does not seem to have waited very long for a seeding event. Some people think life on Earth may have originated within 100 MY of liquid water existing on earth.
On the other hand perhaps transfer opportunities were more common in the early solar system, when planetary impacts were more frequent.

If life were to be discovered in anywhere else in the solar system, this issue will inevitably be brought up.

An important issue would be whether it is something transported from Earth by earthling space probes. However, recent transfers should be revealed by great similarities to Earth life (in DNA sequences, since they would not have much time to evolve great differences).

Earlier (pre-human) transfers (of bacteria or archaea) would have the opportunity (time, a few billion years) to evolve and radiate to different forms/sequences, obscuring any earthly relationships by adapting to their different environment.

A distinct genetic system, that distinguishing Earth life from life that actually arose on other planets would seem to be pretty convincing.
However, a similar genetic system (or parts of metabolism) might not be as convincing an indicator of related origins as one might think.
Some have proposed that early Earth life arose from a mash-up of randomly generated, interacting organic chemicals, making simple prebiotic chemical that became initial (and still in part around) metabolic pathways. The argument is that these initial pathways would arise naturally because they are thermodynamically favored in the environment in which they arose.

 

[member 656954]

However, recent transfers should be revealed by great similarities to Earth life (in DNA sequences, since they would not have much time to evolve great differences).

If we find alien life, is there a way to really distinguish from shared DNA that diverged billions of years ago against actually independently arisen DNA, do you think?

 

[mfb]

The last universal common ancestor of life on Earth lived ~3.5-3.8 billion years ago and has many features that clearly mark all its descendants as related. A nearly identical coding scheme for amino acids is among them. If we find this scheme elsewhere then life is related to Earth.
If life there is linked to us via a much older species that didn't have this genetic code and many other features yet then things can be more difficult. DNA would already be remarkable at least.

 

[pinball1970]

If we find alien life, is there a way to really distinguish from shared DNA that diverged billions of years ago against actually independently arisen DNA, do you think?

Energy systems and Information systems.

 

[jim mcnamara]

There is no really good answer to the problem.
Guesses:
Chirality (stereo-isomers) is a possibility to assert a difference, for example.
Other possibilities include nucleotides that are not based on deoxyribose, for example - for DNA, or other sugars for RNA.

Until we actually get samples (even by robots remotely) , and they are analyzed successfully, it is all speculation, not fact. And we are assuming there is something to find on Mars or Enceladus.

https://solarsystem.nasa.gov/news/863/nasa-study-reproduces-origins-of-life-on-ocean-floor/
https://www.nasa.gov/centers/ames/research/2007/mars_sensor.html

The second link inadvertantly also points out a problem: the time lag for getting appropriate equipment onto tthe Mars surface - why? Article came out in 2007. As we keep learning more exobiology it seems likely that we could determine we are missing something important. But not in a timely way. We see the issues after the test equipment left on a loooong one-way trip. NASA is aware of this obviously.

 

[anorlunda]

If we find alien life, is there a way to really distinguish from shared DNA that diverged billions of years ago against actually independently arisen DNA, do you think?

Must alien life have DNA? That may be an assumption, but I would be surprised if it can be proven. Isaac Asimov once wrote a book on non-carbon-based chemistry that might support life.

 

[BillTre]

If we find alien life, is there a way to really distinguish from shared DNA that diverged billions of years ago against actually independently arisen DNA, do you think?

The DNA synthesizing enzymes are different between the eubacteria (normal bacteria) and archebacteria (Archaea).
Some take this as an indicator that their DNA synthetic systems were not fully set (fully evolved) at time the bacteria and archaea diverged (time of their last common ancestor).
This kind of thing might show the differences you seek.

 

[shjacks45]

Summary:: Life on Europa has been discussed on threads on pf previously. This post relates to models (Jay Melosh) looking at whether life on Europa/Enceladus would be the result from lithopanspermia or from scratch, abiogenesis. Some NASA missions in the pipeline may shed some light on this in the next decade with 'Dragonfly' scheduled for 2026.
This is a summary of one or two points from the American geophysical Union from last week.

https://www.space.com/alien-life-europa-enceladus-second-genesis.html

Titan would be a more logical choice. My vote is to take all of Earths nukes from belligerents the use them to ignite Jupiter. The planet already emits more energy than received from the sun so some reaction is occurring. A brown dwarf would thaw out the satellites.

 

[mfb]

A brown dwarf would need at least ~13 times the mass of Jupiter. There is nothing to "ignite", and throwing a few nuclear weapons into Jupiter does nothing.

 

[Keith_McClary]

The planet already emits more energy than received from the sun so some reaction is occurring.

It is thought to still be cooling from its formation.