Home » An Italian team does the DNA test of asteroids

An Italian team does the DNA test of asteroids

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There are two types of scientific results: those that confirm known theories, inserting new pieces in the mosaic in the right place; and those who, on the other hand, undermine certainties and open up new perspectives; and sometimes it is precisely the results of the second type that bear the best results. This is the case of a research just published in the journal Nature and carried out by a group of scientists from INAF (National Institute of Astrophysics).

Specifically, when NASA’s OSIRIS-REx mission reached the asteroid Bennu in 2018, scientists in America and around the world expected to find a surface covered with fine regolith: a material made up of small grains or pebbles as large as possible. a few centimeters, similar to the sand found on the beaches of our planet. There were similar expectations for the Japanese space agency JAXA’s Hayabusa 2 mission, which reached the asteroid Ryugu in the same year. But once in the vicinity of these two small bodies, both probes revealed rocky terrain, surprisingly covered with boulders and with very little fine regolith.

To us laymen this may seem like a trivial matter, but for specialists it has undermined entire theoretical systems on the nature of asteroids.

Now one led by the Italian researcher Saverio Cambioni, with the participation of Giovanni Poggiali and John R. Brucato of INAF, has solved the mystery: it would be the very porous nature of the rocks of these asteroids to explain the absence of fine regolith on their surface. .

Saverio Cambioni, first author of the article published today in Nature explains: “When the first images from Bennu arrived, we noticed some regions where the resolution was not sufficient to distinguish between small rocks and fine regolith, so we started using our new artificial intelligence method to recognize fine regolith from rocks using the infrared emission recorded by the probe ”.

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Problem: The probe was designed to collect a sample of the asteroid from a surface rich in fine regolith, not between boulders and rocks. Thus, the sampling area on Bennu had to be drastically reduced from a region of about 160 meters, the size of a parking lot for 100 cars, down to 8 meters, comparable to a parking lot for only 5 cars. The operation was successful on 20 October.

The overall appearance of the asteroid Bennu in a mosaic of images taken by the Nasa Osiris-Rex probe.  Copyright: NASA / Goddard / University of Arizona

The overall appearance of the asteroid Bennu in a mosaic of images taken by the Nasa Osiris-Rex probe. Copyright: NASA / Goddard / University of Arizona


“To distinguish the contribution of the fine regolith from that of the rock” explains Giovanni Poggiali, researcher at INAF in Florence “and to make a global study of the surface, it was necessary to put together a large database of regions observed both in the day and in the night. The thermal emission released by the fine regolith, which depends on the size of its grains, is different from the emission produced by larger rocks, which instead depends on their porosity. For this the team simulated the emission produced by different mixtures of fine regolith and rocks of varying porosity, teaching an algorithm how to recognize the different soils and compare them with observations of the Bennu surface ”.

The analysis of the data showed that the fine regolith is not randomly distributed on Bennu but that, where the rocks are more porous – that is, on most of the asteroid – it is systematically found less. This suggests that the highly porous rocks of the celestial body produce less fine regolith because they are compacted – and not fragmented, as is the case with less porous rocks – as a result of meteoric impacts: the cavities inside the rocks would help to cushion the impact of the meteorites. resulting in less fragment production. Furthermore, the porous rocks would break down more slowly due to the diurnal cycle of heating and cooling of the asteroid, further inhibiting the formation of the fine regolith.

An Italian team does the DNA test of asteroids

John Brucato, researcher at INAF in Florence, adds: “With artificial intelligence, used for the first time in this type of research, we were able to go much deeper into the analysis of spectroscopic data, highlighting the unique properties of the materials that constitute primitive asteroids like Bennu and Ryugu ”.

Camboni concludes: “Asteroids are fossils of the formation of the Solar System, but recent studies are showing how in reality some asteroids are very evolved. Understanding the evolution processes of asteroids is important for understanding the evolution of the Solar System and our planet. To shed some light on this, we will need to visit more asteroids in the future to collect samples to be reported and analyzed on Earth. Our study will allow us to understand in advance the nature of asteroid surfaces, and therefore to plan missions accordingly ”.

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