Things that go bump in the night. Meteorites capture some […]

Things that go bump in the night.

Meteorites capture some of the greatest hits of our Solar System, a freeze frame of some colossal collisions pulverizing material deep from within planets and near-planets, creating moons, exploding planets like the Death Star dreamed of, and ejecting entire planets out of our solar system. Here are some of their stories. I finally had some quiet time to pull them together.

Some of my notes:
• 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.”

• 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!”

• 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.”

“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.”

More of my notes from Breakthough Discuss: https://flic.kr/p/2fqVjTs