Scientists have discovered liquid water and organic compounds essential for life on two ancient meteorites that fell to Earth almost 20 years ago.
The research is based on the first ever comprehensive analysis of halite (salt-containing) crystals found within Zag and Monahans, two 4.5 billion-year-old rocks believed to have come from the asteroid belt between the orbits of Mars and Jupiter.
The study, published in Science Advances, appears to support data gathered in the recent years by Nasa’s Dawn spacecraft that suggests building blocks of life may be present on some of the neighbouring asteroids, particularly Ceres, which is the largest object in the asteroid belt.
An international team, including scientists from the Open University (OU) in the UK and Nasa Johnson Space Centre in Texas, found amino acids – which form the basis of proteins, hydrocarbons – organic compounds made up of hydrogen and carbon, and liquid water – the most important ingredient required to support life, within the salt crystals.
The meteorites fell to Earth in 1998 but the technology available at that time did not have the capability to detect traces of amino acids.
Using a combination high-sensitivity mass spectrometers, which detect different molecules based on their size, and NanoSIMS equipment, which uses beams of ions to study the chemical composition of organic materials, the scientists were able to determine the chemical composition of the salt crystals.
Lead author Dr Queenie Chan, a postdoctoral researcher at OU, said: “We collected the tiny salt crystals from the meteorites and dissolved them in water so that we could extract the amino acids and separate any organic compounds to analyse them.
“We conducted our experiments in one of the cleanest laboratories in the world at the Nasa Johnson Space Centre, which avoided any contamination from things such as dust in the air.”
The team used Raman spectroscopy, a technique that uses light to detect the chemical composition of organic materials, to confirm the presence of water.
Dr Chan added: “Each salt crystal, which is about two millimetres in size and the colour of a blue sapphire, is essentially a little package full of organic compounds and the necessary building blocks of life.
“What’s even more incredible is that the salt crystals from both meteorites are believed to be from the largest asteroid in the asteroid belt, Ceres, which suggests that it could be a suitable place for the formation of life.”
The researchers also analysed the chemical composition of the meteorite bodies and found the organic content to be different from those found in the crystals, which led them to believe that the salt crystals may have a different origin to the meteorites.
Dr Chan said: “We believe that the salt may have originated in Ceres or some other carbon-rich asteroid body, while the meteorites come from a different parent body – one that has been heated to 950C so any trace of liquid water present in it would have gone.
“This proves to us the salt crystals and the meteorites come from two different asteroids.
“We believe the meteorite may have come from a stony asteroid, maybe an S-Type asteroid, which are not carbon-rich and are found in the same asteroid belt.”