Chemical markers for bacteria in extraterrestrial samples

Area of Science:

• Astrobiology
• Planetary Science
• Analytical Chemistry

Background:

• Interplanetary missions aim to collect pristine Martian samples for organic molecule and life detection.
• Current extraterrestrial samples (lunar dust, meteorites) face contamination challenges from Earth's atmosphere and storage.
• Distinguishing extraterrestrial organic molecules from terrestrial contamination is difficult, especially concerning bacterial presence.

Purpose of the Study:

• To assess the suitability of lunar dust as a negative control in astrobiological sample analysis.
• To investigate the chemical differences between lunar dust and terrestrial samples using advanced analytical techniques.
• To improve the reliability of searching for organic molecules and signs of life in extraterrestrial samples.

Main Methods:

• Utilized state-of-the-art gas chromatography tandem mass spectrometry (GC-MS/MS) to achieve ultra-low chemical background detection.
• Analyzed lunar fines stored for over 30 years.
• Compared chemical markers in lunar fines with those characteristic of Earth bacteria.

Main Results:

• GC-MS/MS analysis revealed significantly lower chemical backgrounds in lunar fines.
• Lunar fines generally lack muramic acid and 3-hydroxy fatty acids, key markers of terrestrial bacteria.
• Demonstrated a clear chemical distinction between lunar dust and terrestrial dust.

Conclusions:

• Lunar dust, free from terrestrial bacterial contamination markers, can serve as a valuable negative control.
• GC-MS/MS is crucial for reliable analysis of extraterrestrial samples.
• This approach enhances the search for organic molecules and potential life on Mars and in other extraterrestrial samples.