1932

Abstract

The existence of extraterrestrial life was heralded by controversial claims made in 1996 that the Martian meteorite ALH84001 harbored relics of ancient microorganisms. We review here the accumulated evidence for and against past extraterrestrial life in this Martian meteorite. The main pro-life arguments—the presence of polycyclic aromatic hydrocarbons, magnetite crystals, carbonate globules, and structures resembling terrestrial life-forms known as nanobacteria—can be deemed ambiguous at best. Although these criteria are compatible with living processes, each one of them can be explained by nonliving chemical processes. By undergoing amorphous-to-crystalline transformations and binding to multiple substrates, including other ions and simple organic compounds, minerals—especially those containing carbonate—have been shown to display biomimetic properties, producing forms that resemble bacteria. This simple and down-to-earth explanation can account fully for the existence of mineral entities resembling putative nano- and microorganisms that have been described not only in the ALH84001 meteorite but also in the human body.

Loading

Article metrics loading...

/content/journals/10.1146/annurev-earth-042711-105401
2012-05-30
2024-03-28
Loading full text...

Full text loading...

/content/journals/10.1146/annurev-earth-042711-105401
Loading
/content/journals/10.1146/annurev-earth-042711-105401
Loading

Data & Media loading...

  • Article Type: Review Article
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error