Every weekend, an image that made the news or caught our attention. With the repatriation to Earth of samples from the asteroid Bénou, NASA has joined the very exclusive club of nations having collected extra-terrestrial soil in automatic mode.
A resounding success
On September 24, after more than seven years of travel (it was launched on September 8, 2016 from the military base of Cape Canaveralin Florida) and nearly 4 million kilometers traveled, the probe Osiris-REx of the NASA dropped a small capsule near the Earth containing a precious treasure for the scientific community: around 250 grams of samples taken in October 2020 from the surface of theasteroid near-Earth Benou (Bennu, in English).
The probe landed safely in the Utah desert, and was quickly recovered, before being taken to space center Johnson from NASA, to Houston in Texas.
Returns in automatic mode…
It was the Soviets who got the ball rolling on this complex exercise of taking and returning extra-terrestrial soil samples to Earth.
It was with the lunar exploration machines Luna 16 (101 g reported on September 24, 1970), Luna 20 (55 g reported on February 15, 1972) and Luna 24 (170 g reported on August 22, 1976). For a long time these exploits were not republished.
Thus, the probe Genesis which contained more than a million particles of solar wind, had returned to Earth on September 8, 2004, but it was torn apart during the final shock! The success was partial for NASA then in action.
Then, on January 15, 2006 it was the turn of the probe capsule Stardust to return to Earth after collecting more than 10,000 cometary particles from the comet’s tail 81P/Wild. If it was a success, the material collected was precious, but tiny.
More recently, these are the Japanese missions Hayabusa (with its 1,500 grains collected on the asteroid Itokawa on June 13, 2010) and above all Hayabusa 2 (with its 5.4 g coming from the asteroid Ryugu on December 5, 2020), which were resounding successes in this area.
Finally, the Chinese mission Chang’e 5 from the Moon, with its 1,731 g recovered on December 16, 2020, allowed China a remarkable demonstration of its capabilities and mastery.
…are not worth the astronauts’ collections
Obviously, all these probes – and even future ones to come (Chang’e 6, MMX, MSR, Zheng He, Luna 28, Heracles…) – are neither ready to match nor ready to surpass the masses collected by the American astronauts on the Moon during the six Apollo missions.
Between 1969 and 1972, they had in fact reported no less than 382 kg of lunar regolith. Most of it is still stored in an inert atmosphere composed of almost pure nitrogen, at the Lunar Sample Laboratory Facility at NASA’s Johnson Space Center.
Better understand the first moments of the solar system
A sample return mission, whether carried out in automatic mode or by astronauts, makes it possible to meet numerous scientific needs that cannot be met by a study carried out on site by a lander or a rover.
The limited capabilities of a space probe (instrument mass, available energy, instrument sensitivity, number of samples to take and analyze, etc.) only allow it to carry a limited number of instruments, often reduced size.
By having samples on Earth, we can carry out very in-depth analyzes in ultra-specialized laboratories, for example, to date the samples or determine how long they remained in the vacuum of space.
Without a doubt, cosmochemists from all over the world and in particular the French team from the petrographic and geochemical research center in Nancy (CRPG), will be happy to determine the rare gases contained in the samples, after having heated them with lasers, and thus shed even more light on our knowledge of the first moments of the solar system…
Gilles Dawidowicz, a trained planetologist, is vice-president of the Société Astronomique de France