The legendary patience of archaeologists and palaeontologists in making stones and the smallest traces of the past speak is well known. That of astrophysicists is now on a par with them. Among the 5.4 grams of samples recovered in December 2020 from the asteroid Ryugu by the Japanese space agency’s Hayabusa-2 probe, two tiny inclusions less than 100 micrometres wide caught the attention of these fine detectives, mainly Franco-Japanese.
They contain traces of a new chemical compound that bridges the gap between the origins of the Solar System and those of life on Earth. Proud of their find, they even invented a name for their mineral: HAMP, which stands for “oxidized ammonium magnesium phosphorus hydrate.” Which deserves some explanation.
Ryugu is a diamond-shaped asteroid less than a kilometre wide, blacker than coal, very porous and orbiting between 140 and 210 million kilometres from the Sun. Initial studies have shown that its composition is similar to that of meteorites and that it was formed in the first few million years of the Solar System, more than four billion years ago.
“We are dealing with primitive material, little altered, unlike meteorites that have passed through the atmosphere. Its material is for us a terra incognita, rich in discoveries.”explains Cédric Pilorget, professor-researcher at the Institute of Space Astrophysics (IAS) of the CNRS and the University of Paris-Saclay, co-author of the article published on September 25 in Nature Astronomy.
Chemical competence
But these asteroids also left their distant orbits to bombard the forming planets, bringing them a collection of precious chemical elements, such as water molecules, carbon, nitrogen, silicon, or more complex ones, such as amino acids (the components of proteins)…
And possibly also phosphorus, which is not only essential for tooth enamel, but also for more fundamental molecules, DNA, RNA, ATP (which provides energy to cells)… The problem is that this phosphorus, already identified in meteorites, is generally found in a poorly soluble form, therefore not conducive to chemical reactions and the production of all these molecules essential to life.
The importance of HAMPs then becomes clearer. In this new oxidized form (the researchers were unable to determine how many oxygen atoms it is bound to), phosphorus is more soluble and therefore more reactive. Much more so than phosphorus bound to calcium. Its reactivity is made possible by magnesium, water and ammonium, a nitrogen atom bound to four hydrogen atoms.
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