Did Life Come To Earth On An Asteroid?

TL;DR

Panspermia is gaining scientific credibility because experiments show bacteria can survive asteroid-impact pressures and years exposed to the vacuum of space.

Key Points

• 1.A new study found bacteria can survive asteroid-impact pressures. Deinococcus radiodurans was sandwiched between metal plates and hit with pressures up to 3 gigapascals — nearly all survived at 1.4 GPa, and ~60% survived at 2.4 GPa, with DNA-repair mechanisms activating afterward.
• 2.The same bacteria survived years outside the International Space Station. Exposed to vacuum and cosmic radiation, outer layers of microbe colonies died off, forming a natural shield that protected the innermost cells — a self-shielding survival mechanism.
• 3.Tardigrades add further support, surviving extreme space conditions as a complex organism. These ~0.5mm animals endure vacuum, radiation thousands of times lethal to humans, and temperatures down to -200°C, remarkable because they are far more complex than bacteria.
• 4.Lithopanspermia within a solar system is plausible; between solar systems it is extremely unlikely. Rocks ejected by impacts can realistically reach neighboring planets over millions of years, but interstellar travel requires billions of years with near-zero odds of hitting a habitable-zone planet.