NASA arrives in orbit around Ceres, the largest asteroid – BBC

The Dawn spacecraft has traveled eight years in the solar system Friday to place in orbit around this star located between Mars and Jupiter and seen, just as Pluto as a dwarf planet.

After almost eight years of travel in the solar system, Dawn NASA probe will enter orbit around Ceres Friday at 13:20. With a diameter of 970 km and an orbit in the heart of the asteroid belt between Mars and Jupiter, this little-known star is too small to be a full-fledged planet and more spherical and regular than most asteroids. It is also classified as dwarf planets, like Pluto, which is much more distant.

We previously knew of its surface as fuzzy and gray spots, views on best images of Hubble Space Telescope. Approaching Dawn uncovered a body in rugged terrain, dotted with craters. Above all, the American craft detected very surprising bright areas at the bottom of some craters. One of them is even scored two small close points if they saturate the brightest pixel camera Dawn.

Intriguing spots

“We have to wait to see the spectra obtained by Dawn to know for sure what produces these bright spots, but in my opinion the most likely hypothesis is that this ice that appears on the surface, “suggests Antonella Barucci specialist astronomer small bodies of the solar system at the Observatoire de Paris. Carol Raymond, deputy scientific director of the Dawn mission in NASA said Tuesday that these bright spots could be highly reflective materials such as salt or ice.

Last year, the astronomer and his Parisian colleagues had also caused a surprise by detecting with the Herschel Space Telescope of the European Space Agency steam emissions from the surface of Ceres. “It was really surprising because Ceres is in an area previously thought to be too close to the Sun so it can stay in the water as ice,” said Antonella Barucci. The most likely hypothesis is that Ceres formed much farther in the solar system beyond the orbit of Jupiter, before being screened at the heart of the asteroid belt.

Peering in detail the composition of the surface

A story that contrasts sharply with that of Vesta, another large asteroid around which the Dawn probe remained in orbit a little more than a year before to get on the road to Ceres. A little smaller (525 km diameter) and a much battered form Ceres, Vesta has no water on its surface. The two bodies orbit so in the same area, but their stories and their training had to be radically different.

After insertion into orbit, Dawn will first stay at a few thousand kilometers above Ceres, before approaching 400 km altitude, which will examine in detail the composition of the surface.

Meanwhile, the forward will have to be content with images taken by Dawn up ‘March 1. Because the US probe is now at the top of the front night of Ceres, and will fly as a sunny early April.