- March 13, 2015 - Planétarium Rio Tinto Alcan : Astronomical News
Photos are beginning to arrive… the anticipation is so exciting! The Dawn space probe, a mission directed by NASA, is en route to Ceres, the closest dwarf planet to Earth. After travelling more than seven years, the tiny probe was captured by Ceres’ gravity on March 6. Dawn had already observed the asteroid Vesta, in great detail, from 2011 to 2012.
The Dawn of the solar system
Dawn’s primary mission is to understand the processes behind the formation of the solar system, in particular, the origin of the main asteroid belt, situated between the orbits of Mars and Jupiter. To accomplish this, scientists decided to study two asteroids, Vesta and Ceres, which typify the two types of solid objects found in the solar system. Vesta is a rocky world comparable to the terrestrial planets, Mercury, Venus, Earth and Mars; Ceres, on the other hand, is an icy world resembling moons of the giant planets, Jupiter, Saturn, Uranus and Neptune.
Thanks to three instruments, Dawn was able to map Vesta, and now Ceres, to better understand their geology, composition, and both the internal and external forces that governed their formation.
Vesta’s secrets unveiled
From 2011 to 2012, Dawn studied Vesta, the third largest asteroid measuring 530 km across; and it discovered many craters, immense trenches and steep cliffs. The real surprise was an enormous crater in the southern hemisphere, named Rheasilvia: It resulted about a billion years ago from a collision with another asteroid. Material from Vesta’s crust and mantle was ejected into space, confirming the origin of howardite, eucrite and diogenite meteorites found on Earth. Five of these types of meteorite are on display in the Planétarium Rio tinto Alcan exhibition hall.
Ceres, hidden among the asteroids?
Dawn is now approaching Ceres, a dwarf planet measuring 930 km in diameter, and the largest object in the asteroid belt. What is the actual composition of its surface? Some suspect it’s covered in powdered clay. Ceres’ density and spherical shape indicate the presence of rock and ice beneath the surface. Three of the five known dwarf planets have moons: Pluto has five, Eris one and Haumea two. Does Ceres have some hidden moons as well?
An image captured on February 19 reveals a surface strewn with craters, one of which has two bright white spots in the centre. Though no official explanation has been proposed, scientists are considering cryovolcanism (the eruption of ice, rather than lava like volcanoes on Earth). Visit the Dawn mission site and our Facebook page for up-to date photos!