Are we alone in the universe
How to seach for life beyond earth
Find the limits for life on earth -map
How can you hunt for an alien when you dont know what you are hunting for
When I arrived at NASA….
Knew about one planet, and one life form
Today: only one life form. But we know 3900+ confirmed extra-solar planets, 1000+ solar systems, and we are not typical.
If we even had one second life form to tell about, it would be the secular equivalent of ….
We only have one life form, but well worth looking for an alien
We dont even know how long it takes for life to evolve.
It would be like a biologist getting a job in English depart, with only credential that they read a book.
What is life?
We dont even have a good definition of this.
Sneaky trick for audience love: show a slide with a puppy to get oooh and aaaah
Non natural definition - da Vinci definition of water.
We are still at the da Vinci stage of the definition of life.
Maybe there is something essential about it? We dont know.
So we have a operational definition
Why carbon?
strong argument it is only possible basis
Composition of earths crust
Our relationship to electromagnetic spectrum is determined by carbon
Fabulous place for life, but the lakes are carbon ethane/methane. Too cold to support organic life.
Sometimes lecture the Vatican - titan placed in solar system to test our faith in water based life
Operational definition
The universality in principal of natural selection
Abiotic sources for amino acids.
Sources:
making peptides abiotically. A way to form peptides on silicates, earth crust is 90% silicates.
Impact synthesis
Ingredients for life:
RNA - bases found in abiotic settings Plausible routes to nucleotides. Polymerization can occur wth activated monomers, and up to 100mer without activated monomers between lipid bilayers
None of these are anything special
Abiotic and agnostically
DNA - “not so easy, so we wont talk about that.”
The discoveries in astrochemistry and prebiotic chemistry say “yes”
Argue from convergence
Independent evolution of the same solution.
Cactus, roses, rear end of a porcupine - exactly the same message in nature: dont eat me you will be sorry
Great moments in evolution
Could photosynthesis evolve again?
With autotrophy, life was able to go beyond reliance on abiotically produced organic carbon
Or sun is essentially limitless energy
Physical environment
Biological
Solar radiation map of earth - we lose so little
Light harvesting pigments
Reductants
Carboxylating enzymes
The origin of eukaryotic cell by primary and secondary endosymbiosis
Primary host - red alga - secondary host - cryptomonad
Some look for stupid life, others for intelligent life
Multicellaularity is not as great an achievement as we are lead to believe.
Tree of life: bacteria, archaea, eukarya
single sell - diffusion problems - gases cant penetrate, easier if small building blocks
Organisms tried to go to the land many times
Skin color is an adaptation to solar radiation, and not a badge of identity.
Where the intensity is highest is where you see the darkest skin
Skin cancer is post reproductive - evolution is pressure for something before reproduction
Neural tubes need folate, and folate is sensitivity to UV. We also need vitamin D from solar, so we need to absorb enough to synth Vitamin D, but not break down folate.
Pale skin to get enough vitamin D for proper bone development.
Why evolve it?
Artemis was Apollo’s twin sister
A quick divergence to mammalian biology
Afrotheria Atlantogenata Eutheria Boreoutheria Xenarthra
Etc.
Where is intelligence found:
Ant eating- convergent
Or eventually, will we make life de novo?
With engineering we can explore things that might happen elsewhere
Can put things in vesicles now, and they can make proteins. Is that life yet?
Average person thinks big gap is microbes to humans. No it is still non-life to life. Life is very complex.
So back to the original question: is there a universal biology?
Arguments from convergence seems to indicate yet.
Would aliens look like us?
Divergence - organism using tools in the toolkit
Each divergent uses different toolkits to build the same feature
Last universal common ancestor
Question: if you have certain complexity in a molecule, left handed and right handed molecules. Why do we use one hand vs. the other.
One idea is it was an accident that gets the secondary and tertiary structures
Another idea - bias from circularly polarized light, more of one precursor or the other
Question: interstellar panspermia
Rocks can go from planet to planet. LH4401
Announced same day as someone won the nomination for Republican Party. Not a coincidence
Interplanetary exchange between mars and earth is known.
Could you get a life form ejected, survey journey, survive impact
My class clown thoughts: