life-off-earth.pptx

SETL
The Search for Extraterrestrial Life
(in our solar system)
By CactiStaccingCrane - Own work, CC BY-SA 4.0,
https://commons.wikimedia.org/w/index.php?curid=117012949

All Around the
World
• Curtis “Ovid” Poe
• https://allaroundtheworld.fr/
• https://fosstodon.org/@ovid
• https://twitter.com/OvidPerl
• ovid@allroundtheworld.fr
15/08/2023 © 2023, All Around the World https://allaroundtheworld.fr/

Image Credits
Unless otherwise credited, images are public domain from NASA,
or PowerPoint stock images.

Question
Policy
15/08/2023
© 2023, All Around the World
https://allaroundtheworld.fr/

Are We Alone?
• Anaxagoras, 5th century BCE, moon was inhabited
• Epicurus, 4th century BCE, letter to Herotodus
• Lucretius, 1st century BCE, De Rerum Natura
• Plutarch, 1st century CE, De Facie Quae In Orbe
Lunae Apparet
• … and many more

You Are Here

What is life?
Is there a common chemical model for life in the
universe?
Steven A Benner, Alonso Ricardo and Matthew A
Carrigan
https://www.researchgate.net/publication/8171722_

Biopresentation
• There is no “life detector.”
• Are viruses alive?
• Or merely a chemical process?

Spectrum
Biology Chemistry Physics ???

Biopresentation
• Reproduction
• Homeostasis
• Growth
• Metabolism
• Reaction to stimuli
• Communication
• …

Biopresentation
• Assembly theory?
• Autocatalytic sets?

Life is Hard
• We can’t define life
• So we can’t identify life
• This is a hard problem

The Drake Equation
• Created by Dr. Frank Drake in 1961
• A thought experiment
• How many dectable, active, communicative civilizations?
By Amalex5 - Own work, CC BY-SA 4.0

N = 𝑅∗ • 𝑓𝑝 • 𝑛𝑒 • 𝑓𝑙 • 𝑓𝑖 • 𝑓𝑐 • L
• R∗ = Stars formed per year
• fp = Fraction of those with planets
• ne = Number of planets of those which can support life
• fl = Fraction of those which have life
• fi = Fraction of those which have intelligent life
• fc = Fraction of those which can communicate
• L = Civilization lifespan

N = 𝑅∗ • 𝑓𝑝 • 𝑛𝑒 • 𝑓𝑙 • 𝑓𝑖 • 𝑓𝑐 • L
None of these numbers were known in 1961.

Original Estimates
• R∗ = Stars formed per year (1)
• fp = Fraction of prior with planets (20% to 50%)
• ne = Number of planets (1-5)
• fl = 100%
• fi = 100%
• fc = 10% to 20%
• L = 1,000 to 100,000,000 years
20 to 50M communicating civilizations

N = 𝑅∗ • 𝑓𝑝 • 𝑛𝑒 • 𝑓𝑙 • 𝑓𝑖 • 𝑓𝑐 • L
• R∗ = Stars formed per year (6-7)
• fp = Fraction of prior with planets (50% to 100%)
• ne = Number of planets per prior which can
support life (1?)
• fl = Fraction of prior which have life
• fi = Fraction of prior which have intelligent life
• fc = Fraction of prior which can communicate
• L = Civilization lifespan

SETL
Search for Extraterrestrial Life
(*as we know it)

Moons are planets:
Scientific usefulness versus cultural teleology
in the taxonomy of planetary science
https://www.sciencedirect.com/science/article/pii/S0019103521004206

By NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill - Ganymede - Perijove 34 Composite, CC BY 2.0 By NASA/Johns Hopkins University Applied Physics Laboratory/Arizona State University/Carnegie
Institution of Washington - https://photojournal.jpl.nasa.gov/catalog/PIA11364, Public Domain

Sources?
• They’re all over the (galactic) map
• Citing a specific sources might give too much credence
• Tried to pick “acceptable” numbers

Intelligence?
• When earth was inhabitable
• First life
• First multicellular life
• First intelligence

First Life
Earth forms ~4.5 Gya (giga, or “billion,” years ago)
Can support life ~4.3to ~4 Gya
Life arises ~4.3 to ~3.8 Gya

Multicellular
Life
• ~0.6 Gya: macroscopic multicellular
• Life started very early
• Over 3 billion years for complex
multicellular life to evolve
• Lots of controversy

Intelligence?
• ~.5 Gya
• Cetaceans
• Corvids
• Cephalopods

Rough
Timeline
• Life arises almost instantly
• 3 Gya: multicellular
• .6 Gya: complex multicellular
• .5 Gya: intelligence
Lots of controversy

Intelligence
Intelligence might be common for
complex multicellular life

Sample Size
N=1

Signatures
• Biosignatures
• Technosignatures
By Kevin Gill from Los Angeles, CA, United States - A Dyson Swarm Superstructure, CC BY 2.0,

NASA
ASTROBIOLOGY
STRATEGY 2015
1. Isotope patterns
2. Chemistry
3. Organic matter
4. Minerals
5. Microscopic structures and textures
6. Macroscopic structures and textures
7. Temporal variability
8. Surface reflectance
9. Atmospheric gases
10. Technosignatures

End Background
• Lots of questions
• Few Answers
• It’s a hard problem

Life in Our Solar
System
• Many excellent candidates
• Forget “organic molecules”
• We might not recognize it

ALL THESE
WORLDS ARE
YOURS –
EXCEPT
EUROPA.
ATTEMPT NO
LANDING
THERE
15/08/2023

Europa
• 4th largest Jovian moon
• Probably a subsurface ocean
• Arthur C. Clarke–2010: Odyssey Two

Europa
• Poor in biosignatures
• Hydrothermal vents?
• JUpiter ICy moons Explorer
• Europa, Ganymede, Callisto
• 2023 launch
• 2031 arrival
• NASA Europa Clipper
• 2024 launch
• 2030 arrival

Enceladus

Enceladus
• 6th largest moon of Saturn
• Subsurface ocean
• Methane

Orbilander
• Proposed to launch in 2038
• Arrive in 2050
• 200-day orbit
• 2 samples per day
• Then landing on Enceladus

Titan

Titan
• Largest of Saturn’s moons
• Liquid hydrocarbon lakes
• -179°C (-290°F)

Titan
• Should be acetylene, but there’s not
• Hydrogen disappearing on the surface
• Independent source of life?
• Assume abiotic processes
Life on Titan? New clues to what's consuming hydrogen, acetylene on Saturn's moon
https://www.sciencedaily.com/releases/2010/06/100606103125.htm

Titan Mission:
Dragonfly
• Launches in 2027
• Arrives in 2034
• Quadcopter to visit multiple sites
• Studies prebiotic chemistry

Dragonfly Mission
Landing Sequence
Animation

Venus

Venus
… is a hellhole.

Venus
• 92x atmospheric pressure
• ~470° C (~880° F) surface
• Sulfuric acid clouds

Phosphine
(PH3)
• Earth anaerobic biosystems
• Should degrade in Venus
atmosphere
• No known abiotic production*
• Existence controversial

Life on Venus?
• ~4Gya water on Venus?
• Possibly could support life
• Extremophiles

Extremophiles
• Thermus aquaticus, Tom Brock,
1969
• Temperature extremes
• pH extremes
• Ionizing radiation
• … and more

Venus
Extremophiles?
• 10m below surface, 200°C?
• Clouds?
• Venera 13 “mushrooms” (hint: no)
Objects of Hypothetical Life on Venus at the Venera Landers Sides
LV Ksanfomality*, AS Selivanov and Yu M Gektin
International Journal of Earth Science and Geophysics
https://biocoreopen.org/ijbb/Hypothetical-Life-on-Venus-Objects-of-unidentified-Nature-at-Venera-9-and-Venera-13-Landing-sides.pdf

Venus
Clouds
• 60km (36 mi), Earthlike
pressure and
temperature
• 1967, Morowitz and Sagan
• “Unknown absorbers”
(dark patches)
• “difficult to explain …
inorganically”
15/08/2023
© 2023, All Around the World https://allaroundtheworld.fr/
Life in the Clouds of Venus? Morowitz, Sagan, 1967
https://www.nature.com/articles/2151259a0
Mysterious dark patches in Venus’ clouds are affecting the weather there
https://astronomy.com/news/2019/08/mysterious-dark-patches-in-venus-clouds-are-affecting-the-weather-there
The Astronomical Journal: Long-term Variations of Venus's 365 nm Albedo
Observed by Venus Express, Akatsuki, MESSENGER, and the Hubble Space Telescope
https://iopscience.iop.org/article/10.3847/1538-3881/ab3120

Mars
15/08/2023

Martian
History
• Oceans ~4.5 Gya ?
• Maybe habitable before Earth
• Asteroid impacts, amino acids

Mars Today
• Curiosity, Perseverence, Zhurong
• Seven operational orbiters
• Bottom of Earth’s oceans

Martian
“Fossils”?
• 1996 McKay, Gibson,
Thomas-Keprta
• ALH84001, oldest Martian
meteorite
• Microbial fossils?

Martian
“Fossils”?
• Magnetite crystals
• Carbonate globules
• Organic molecules
• The photo =>

Martian
“Fossils”?
• Magnetite crystals can be
formed by shockwaves
• Too small/contamination
• Restarted Mars
Exploration Program

Methane
• Strong biosignature
• Degrades quickly
• Detected by Curiosity
• Strong seasonal variation
Mars methane rises and falls with the seasons
https://www.science.org/doi/10.1126/science.359.6371.16

https://mars.nasa.gov/layout/embed/image/mslweather/

What is going
on?
• No known explanation
• Biology could explain it
• Assume that it’s not

Viking Landers

Viking 1 & 2
• Viking 1 lander, Chryse Planitia, August 7, 1976
• Viking 2 lander, Utopia Planitia, September 3, 1976
• 6,460 kilometers (4,014 miles) apart

Gas chromatograph—mass spectrometer
• GCMS measured few significant organic molecules
• Except chloromethane and dichloromethane
• Contaminants from cleaning materials?
• May be a result of percholorates
• Note: GCMS frequently failed when tested on Earth
Journal of Geophysical Research: Planets
Reanalysis of the Viking results suggests perchlorate and organics at midlatitudes on Mars
Navarro-González, Vargas, de la Rosa, Raga, McKay
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010JE003599

Labeled Release (LR)
• First tested on Earth
• Injected Martian soil with nutrient solution
• Monitored air for metabolic byproducts (via radioactive carbon-14)
Mars methane rises and falls with the seasons
https://www.science.org/doi/10.1126/science.359.6371.16

• Both lander samples tested positive for metabolism
• Significantly less activity at 50°C increase
• Both samples tested negative above 160°C increase
• No activity when stored at 10°C for two months
Did 40-year-old Viking experiment discover life on Mars?
https://phys.org/news/2016-10-year-old-viking-life-mars.html

Formate
• Formate can replicate result with nearly sterile soil
• No sterilization control experiment
• Probably very little formate on Mars

Perchlorate
• Detected on Mars in 2009
• Could also produce positive results with LR
• But do not break down at 160°C

Hypochlorite
• Cosmic rays/solar radiation might break perchlorates into hypochlorite
• Could also produce positive results with LR
• They do break down at 160°C

Hypochlorite
• Best abiotic candidate for LR results
• Never tested at 50°C
• Never tested with long-term dark storage

• No abiotic process demonstrably replicates results
• 2nd and 3rd injections did not release the labeled gas
• Other chemicals might replicate results
• We may have discovered Martian life in 1976
• Most scientists say “no life”
The Case for Extant Life on Mars and Its Possible Detection by the Viking Labeled Release Experiment
Levin, Straat
https://www.liebertpub.com/doi/full/10.1089/ast.2015.1464

Summary
• Many places can support life
• Lots of hints, no proof
• “Get your ass to Mars!”

Planning
1. Risk
2. Reward

What Would
Extraterrestrial
Life Mean?

Not much

Not much, but it can
nurture the soul

Possibilities
• Unknown origin
• Common origin
• Separate origin

No Common
Origin?
• Methane-based (Titan!)
• Carbon-based, but no DNA/RNA
• Wrong chirality

N = 𝑆∗ • 𝑓𝑝 • 𝑛𝑒 • 𝑓𝑙
• S∗ = Number of stars which exist
• fp = Fraction of those with planets (50%+)
• ne = Number of those which can support life (1?)
• fl = Fraction of those which have life

N = 𝑆∗ • 𝑓𝑝 • 𝑛𝑒 • 𝑓𝑙 • L
No matter how you adjust
these numbers, the universe
is teeming with life

Which came first:
The chicken or the
metabolism?
• Autocatalytic chemical networks at the origin of
metabolism
• https://royalsocietypublishing.org/doi/10.1098/rsp
b.2019.2377
• Sets of chemicals which can reproduce themselves
• They metabolize, but aren’t “alive”
• If autocatalytic sets are common, life might be
unavoidable
Image courtesy amazon.com. Used under “Fair Use”

Questions?

Assembly Theory
• How many steps to create a molecule?
• Assembly index of 15 is our cutoff
• Ethyl formate and n-propyl cyanide 3 (seen in space)
• Tryptophan 11/12 (maybe seen in space)
• Adenine 7
• Penicillin 17
• ATP 21

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