In 2020, NASA's Curiosity rover drilled into ancient Martian clay and used one of its two precious chemical tools to study the powder. Six years later, scientists finally revealed what they found.
Curiosity detected 21 carbon-bearing organic molecules in a sample of Martian rock, including seven never before seen on Mars. One molecule was a nitrogen heterocycle, a ring-shaped structure similar to the building blocks of RNA and DNA. This had never been confirmed on the Martian surface before.
The sample, named Mary Anning 3 after a 19th-century fossil collector, came from Glen Torridon, a clay-rich trough on Mount Sharp in Gale Crater. Billions of years ago, this area was a lake or stream. The clay preserved organic molecules for approximately 3.5 billion years.
To extract the molecules, Curiosity used TMAH, a chemical reagent that helped a mass spectrometer read the data. This was the first wet chemistry experiment performed on another planet.
However, scientists cannot determine where these molecules originated. They could be evidence of ancient Martian life, products of lifeless geology, or material from meteorites that fell on Mars, similar to rocks that helped create life on Earth.
The discovery suggests Mars's surface can preserve life's ingredients for billions of years if proper minerals protect them. This makes clay deposits like those at Glen Torridon important targets for future missions searching for signs of past life on Mars.