Complex molecules are not just found on Earth. Various space environments from the atmospheres of moons, to comets and interstellar nebulae, are home to large and important molecules. Now, a team of scientists are claiming a new one might soon join the ranks.

Reporting in a yet-to-be peer-reviewed paper available on the pre-print server arXiv, researchers have found evidence in a meteorite of what they say may be the first protein found from outside Earth. The work details the use of a state-of-the-art analysis on the meteorite Acfer 086, found in Algeria in 1990, and the Allende meteorite found in Mexico. After drilling the meteorites for pristine samples, they added liquid to the resulting powder to turn it into gas and study using high precision mass spectrometry. The researchers found amino acids, as well as a protein containing both iron and lithium that they have dubbed hemolithin.

“This is the first report of a protein from any extra-terrestrial source,” the authors wrote in the paper. But while proteins are key for life, it doesn’t mean that the existence of this molecule implies alien life elsewhere.

Proteins are particular chains of amino acids connected by a peptide bond, a link between a carbon and nitrogen atom specific to amino acids. Amino acids have been described as the building blocks of proteins and they are no strangers to outer space. They have been discovered in both meteorites and comets before, including Acfer 086, but the complexity and length of this newly discovered molecule suggests this is something more.

The obvious question is could the samples have somehow been contaminated on Earth? To try and rule that out, the team looked at the isotopic composition of the hydrogen in the molecule. Hydrogen can come in three forms or isotopes: your regular type with a single proton in its nucleus; deuterium, which has a proton and a neutron; and tritium, which has one proton and two neutrons. The ratio of regular hydrogen to deuterium on Earth is very well defined and also very different from what it is seen in comets and in outer space. The hemolithin in this study is reported to have a ratio close to that observed in comets, which suggests that it is not from Earth.

It has previously been suggested that proteins need the presence of water to maintain their structure, which complicates their survival in outer space, but clearly there are caveats if hemolithin can form and stay that way.  

If this is the first evidence of a protein from outer space that would be very exciting, but some scientists are skeptical about the results. So in the meantime, we'll look forward to the peer-reviewed version of this work, and more investigations on this and other meteorites.