Scientists analysing 120 grams of material returned from a near-Earth asteroid have identified more than 20 amino acids and several nucleobases, the chemical building blocks of proteins and genetic material. The find strengthens the hypothesis that the raw ingredients of life were delivered to the early Earth by asteroids and comets.
We did not find life. We found the parts list. And the parts list is older than the Earth itself.
- Dr. Samuel Ochieng, astrobiologist, Institute for Planetary Science
Because the sample was collected in space and sealed before re-entry, researchers are confident the organic molecules are extraterrestrial rather than contamination picked up on the ground - a persistent problem with meteorites recovered after they fall.
What was in the sample
The material dates to roughly 4.5 billion years ago, older than Earth, and preserves chemistry from the solar system's formation. Alongside amino acids, the team reported nucleobases found in DNA and RNA, and evidence of past liquid water in the parent asteroid.
Why the delivery mechanism matters
The six-year sample-return mission was designed precisely to answer the contamination question. Finding these molecules in a pristine sample makes the case that similar chemistry rained onto the young Earth in vast quantities, seeding the environment where life later began.