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.

• our definition is simple: H2O

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

• life is an emergent process based on physical components, not just an object
• the recess includes fighting entropy a la shroder

Why carbon?

strong argument it is only possible basis

1. A lot of carbon - 4th most common
2. periodic table showing relative amounts of elements - the most common elements critical in life
3. we use metals - look at back of vitamin bottle - an aweful lot of trace metals we use. Carbon organic metal based.
4. the key is carbon

1. it is forth most common element in the univers
2. eit is capable of making DNA
3. atomic carbon and simple compounds with up to 13 atoms have been either detected in interstellar space or produced in laboratory simulations, including amino acids and nucleotide bases

Composition of earths crust

1. lots of oxygen
2. over 90% is silicate - we are perfect place for silicon life to evolve, but we still have carbon based life

Our relationship to electromagnetic spectrum is determined by carbon

• prebiotic chemistry DNA repair, damage / mutation; aging reactive oxygen specieis

• only beverage we have to have
• really good as a solvent because f its widespread occurrence and the chemical properties of water including that it is liquid at a higher temperature than the alternatives
• using alternatives at a low temperature means chemistry proceeds at very slow rate
• frozen - floating - ice covered moons, with liquid water beneath them, like europa
• lots of water throughout the solar system

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

• you are going to look similar to your parents
• things will happen you cant personally srvive

Abiotic sources for amino acids.

Sources:

• Meteorites
• star dust
• (others)

making peptides abiotically. A way to form peptides on silicates, earth crust is 90% silicates.

Impact synthesis

• enough to synthesize short proteins

Ingredients for life:

• polymers
• Lipid can form abiotically and self-assemble into vesicles

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

• each arrived independently
• others: evolution of wings - seem to be something that can come up periodically

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

• energy in the form of light
• inorganic carbon

Biological

• light harvesting pigments
• reluctant - its of possibilities, including ater
• carboxylation - taking CO2 and putting on another enzyme

Solar radiation map of earth - we lose so little

Light harvesting pigments

• chlorophyll and bacteriochlorophylls
• carotenoids
• rhodopsins halophilic arhaea
• retinals
• phycolibins

Reductants

• water - bacteria, plants

Carboxylating enzymes

• 18 of them
• (spell correct: purification magic) pyruvate malic caboxylase

The origin of eukaryotic cell by primary and secondary endosymbiosis

Primary host - red alga - secondary host - cryptomonad

• this happens over and over again - one creature swallowing another than figured out how to do it

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

• multicellar taxa are tiny tiny end of the branch

• bigger harder to be eaten

single sell - diffusion problems - gases cant penetrate, easier if small building blocks

• coordinate movements
• senescence — we dont worry about a few cells dying

• ratcliff et. Al. 2012 Experimental evolution of multicellularity, PNAS
• keep breeding the yeast that fell to the bottom
• snowflake phenotypes - globs with about 30-40 cells, seemed to be heritable
• some think ancestors of yeast were multi-cellular

Organisms tried to go to the land many times

• escape predation
• big impetus: plants & animals - as you get warmer, liquid doesnt hold as much gas. Oxygen starved - getting oxygen you need is to gulp from air, or moving to land.

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?

• predation requires movement and sensory ability
• prey need to avoid being eaten
• our strategy dealing with highly variable environment

Artemis was Apollo’s twin sister

A quick divergence to mammalian biology

Afrotheria Atlantogenata Eutheria Boreoutheria Xenarthra

Etc.

Where is intelligence found:

• primates
• dolphins
• afrotheria
• octopus - very intelligent

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

• there seems to be a branching very early - distinct metabolically

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

• predictive power

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

• every step possible
• problem is transit time - long time with no metabolism damage just accumulates - interstellar probably not possible

My class clown thoughts:

• Solar system - should be renamed the social system.