Breakthrough Discuss 2019 — Migration of Life in the Universe

At the brain spa on panspermia in Berkeley today, I am sitting next to Pete Worden, who I first met at his astrobiology conference at NASA in 2002, and Natlie Batalha, seen here giving the opening keynote with conclusions from the Kepler exoplanet hunting mission. She was the first to discover an Earth-like planet circling a distant star. So many exiting sessions — I’ll share some summary notes here and you can watch it live today here.

“Humanity may well be on the verge of discovering life elsewhere in the Universe. We will want to know if we share a common origin: was this life transferred to or from Earth, or did life arise independently on each world? The possibility that life can or might be transported among planets, star systems, and galaxies frames the major questions being explored at Breakthrough Discuss 2019.

A decade of exoplanet discoveries has revealed that, statistically, about 25% of stars host at least one temperate rocky planet of around one-to-four Earth radii – just right for life as we know it. Perhaps life could evolve independently from simple chemistry on each of these planets. But ample evidence exists for comet or meteor strikes on planetary surfaces transferring material between the planets in the Solar System. This raises the possibility of life as a communicable microbial infection between planets. And the exchange of life between planets could even be galactic in scope: the surprising discovery of abundant Neptune-sized exoplanets at small orbital radii, where they are unlikely to have formed, suggests that large planet migration is common – and that this would result in the frequent ejection of other planets from these systems. Such interstellar rogue planets are an ideal vehicle for the transfer of life across the galaxy. The interstellar object ‘Oumuamua may be an example of such an ejection. Is there sufficient movement among planetary and interstellar bodies for life to migrate between them? Can life survive interplanetary, or even interstellar transit?

Astrobiology dogma assumes that life evolved from a primordial soup of chemicals on the early Earth via an RNA world to the current DNA world. But an alternative view is that these steps occurred on another planetary body more than 4 billion years ago, and that highly-evolved DNA-based life seeded the Earth as soon as it was habitable. If complex microbial life has been transferred between planets and planetary systems, the single-molecule sensitivity tools of modern genomics can be used to detect life. SETI projects can also look for DNA sequences in aperiodic transmissions. Migration of DNA-based life between star systems could be a simple natural phenomenon, or it could have been directed, just as terraforming by microbial inoculation may be the next step in the colonization of Mars. And if life on Earth was intentionally seeded, are there messages embedded in genomes for the evolved molecular geneticists and astrophysicists, 4 billion years later, to decode?”

Drew Endy (Stanford Bioengineering and iGEM and Gen9 (I was investor)): “Should We Search for Messages from Extraterrestrial Intelligences in Terrestrial Genomes? Compared to other methods of interstellar messaging, DNA-encoded messages could have the advantages of being auto- amplifying and blanketing across space and time (i.e., everywhere and persistent).”

Lindy Elkins-Tanton (ASU, NASA Psyche and a stealth lunar project we are working on): “Could life arise on small bodies? In particular we are interested in planetesimals that grew rapidly in the earliest years of the solar system to hundreds or thousands of kilometers in radius. A short-lived radioisotope of aluminum (Al-26) provided sufficient heat for the formation of liquid water (and in some cases, temperatures sufficient to melt silicates), and asteroids show that a wide variety of organic matter was also available. Comets and rogue planets are also candidates to harbor warm, organic- rich environments with liquid water.”

“The Murchurion meteorite has 10’s of thousands of organic molecules and 35 amino acids. It is so full of organics that when I sniffed it, it smelled like a sulfurous oil well. Life flourishes underground. We should send drills everywhere!”

Kat Volk (U. of Arizona): “Planetary rearrangements are probably responsible for ejecting large numbers of planets and small bodies into interstellar space, facilitating the transfer of material between planetary systems. The population of icy Kuiper belt objects orbiting beyond Neptune in the outer solar system provides strong evidence that our giant planets did not form in their current locations but instead arrived on their current orbits as a result of planetary migration. During migration, several tens of Earth masses of material were likely gravitationally scattered around the solar system, with most of that mass being ultimately ejected into interstellar space.”

“Did we lose a planet? Our Solar System looks to have had a 5th giant planet 10-30x the size of Earth that was ejected.”

“Cassini revealed that Saturn’s rings might be only 150M years old.”

Sara Walker (ASU-SFI): “Life is about information. We can quantify life by a transition in the information properties of matter. Life is an emergent property of chemical networks.”

Benjamin Weiss (MIT): “The lithopanspermia hypothesis posits that life could be transferred between planets in the solar system by meteorites. The identification of more than 130 known meteorites from Mars beginning in the 1980s demonstrates that geologic materials have been naturally transferred between the planets by meteoroid impacts. Petrological and geochronological studies over the last two decades have established that many Martian meteorites were transferred from Earth without being heated above 100C. Because this process was probably most efficient prior to 3.9 billion years when Mars may have had a habitable climate, it is conceivable that the origin of Earth’s life occurred on Mars.”

“The transport of material from Mars to Earth is 50x Earth to Mars because of gravity. If you want to look for a Martian, one place to look is in the mirror!”

So exciting… I happen to have the 2nd largest Martian meteorite on display at work. 🙂

Steinn Sigurðsson (Penn State) on Lithopanspermia: “The hydrodynamics of the ejection process allows for relatively gentle ejection of mesoscale pieces of crustal material, which can harbor biota. Some ejecta, including entire moons and planets, may reach stellar escape velocities and wander through interstellar space, with a finite probability of entering other planetary systems and transferring biological material between stellar systems. I briefly review some of the relevant processes, timescales and approximate probabilities for transfer of material between stellar systems.”

“We model 10^11 ʻOumuamua-like ejected objects per cubic parsec, which implies one/month entering our solar system, and if 3% are captured by Jupiter then 10^10 have entered our solar system. In total, 100 should have hit Earth.” These are inbound from distant solar systems.

Jay Melosh (Purdue): “Spores do better in a vacuum than in a wet environment. The DNA wraps around a histone to protect it, and there is some evidence that they may have survived 250M years. Why do we have this property in our DNA? Why do we tolerate a vacuum so well? Why did we need that?”

Gary Ruvkun (Harvard): “While astrobiology dogma assumes a primordial soup of chemicals on early Earth that evolved via an RNA world to the current DNA world, these steps could have occurred on another planetary body more than 4 billion years ago and a highly evolved DNA-based life could have seeded the Earth as soon as it was habitable. Supporting a microbial transfer model is the fact that many protein sequences were already evolved to their modern state in the universal ancestor to the tree of life soon after the cooling of the Earth. All known organisms on Earth share a core of about 500 genes, including the most conserved of those genes, the 16S ribosomal gene, some or all of which were inherited from a common ancestor. This common ancestor has been hypothesized to be an archaeal- like hyperthermophile 3 to 4 Ga ago whose metabolism exploited oxidation/reduction gradients.”