Origin of alkylphosphonic acids in the interstellar medium

Area of Science:

• Astrobiology
• Organic Chemistry
• Planetary Science

Background:

• The origin of phosphorus in early life is a long-standing puzzle.
• While modern life uses phosphate (P(+V)), its low bioavailability suggests earlier life may have used more soluble P(+III) compounds.
• The extraterrestrial synthesis of these P(+III) precursors has not been well understood.

Purpose of the Study:

• To investigate the potential for synthesizing soluble organic phosphorus compounds in extraterrestrial ices.
• To explore the role of galactic cosmic rays in prebiotic phosphorus chemistry.
• To identify plausible pathways for delivering prebiotic phosphorus to early Earth.

Main Methods:

• Laboratory simulation experiments involving interstellar ice analogs.
• Doping ices with phosphine (PH3) and exposing them to conditions simulating galactic cosmic ray irradiation.
• Analysis of the resulting organic phosphorus products.

Main Results:

• Efficient generation of three simple alkylphosphonic acids (soluble P(+III) compounds) was observed.
• These compounds formed in phosphine-doped ices upon interaction with simulated galactic cosmic rays.
• Demonstrates a facile extraterrestrial synthesis route for prebiotic phosphorus organics.

Conclusions:

• Galactic cosmic ray irradiation of interstellar ices provides a viable pathway for synthesizing key phosphorus precursors.
• This mechanism offers a plausible source for phosphorus incorporated into early life.
• These molecules could have been delivered to Earth via comets and asteroids.