New study casts doubt on theory about the role comets played in kick-starting life on Earth

Key Points:

• New computer simulations challenge the long-standing theory that comets delivered key organic molecules to Earth, suggesting these molecules would have been destroyed upon impact due to high velocities and pressures.
• The study, published in Scientific Reports, simulated over 100,000 comet impacts during Earth's early heavy bombardment period and found that successful delivery of intact life-starting molecules was highly unlikely.
• Hydrogen cyanide (HCN), a crucial precursor for prebiotic chemistry found in comets, would have been mostly destroyed or diluted upon impact, and other necessary elements like phosphorus and sulfur are rarely present in comets.
• Alternative origins for life's building blocks include synthesis within Earth's primordial environment or delivery by slower, more numerous asteroid impacts, with recent asteroid sample analyses supporting this possibility.
• The findings also suggest that Mars, with lower comet impact velocities, may have been a more favorable environment for preserving comet-delivered organic molecules, adding a new dimension to the search for ancient life on the red planet.