Extraterrestrial organic matter: a review

Area of Science:

• Astrobiology and Organic Chemistry
• Planetary Science and Astromaterials

Background:

• Organic molecules are prevalent in the interstellar medium (ISM) of the Milky Way Galaxy.
• Over 100 organic molecular species have been identified in the ISM via radio spectroscopy.
• Heavier organic molecules, like polycyclic aromatics, are also present but not individually identified.

Purpose of the Study:

• To review the nature and origin of widespread organic material in the Milky Way and Solar System.
• To examine the links between interstellar organic matter and material found in primitive Solar System objects and early Earth.
• To assess the preservation and delivery of prebiotic organic molecules to Earth.

Main Methods:

• Review of spectroscopic data from the interstellar medium.
• Analysis of organic material composition in carbonaceous chondritic meteorites.
• Examination of cometary volatiles and their relation to interstellar species.
• Assessment of accretion processes involving asteroids, comets, and interplanetary dust particles.

Main Results:

• Organic material is preserved from interstellar cloud collapse to Solar System formation.
• Carbonaceous chondrites contain up to 5% organic material, including amino acids and nucleobases.
• Cometary organic matter is abundant but poorly characterized, sharing species with the ISM.
• Interplanetary dust particles of cometary origin are likely the primary source of intact prebiotic organics delivered to Earth.

Conclusions:

• Organic material has a continuous history from the interstellar medium to the early Earth.
• Asteroids and comets served as significant reservoirs and delivery vehicles for organic compounds.
• The accretion of cometary dust particles was crucial for delivering intact prebiotic molecules to Earth.