After a seven-year cruise, and a one-year successful mission at the giant asteroid 4 Vesta, NASA’s Dawn space probe today successfully entered the orbit of its second and final target, the dwarf planet Ceres.
Dawn will use its ion propulsion system to change orbits at Ceres, allowing it to observe the dwarf planet from different vantage points. Image credit: NASA / JPL.
Located in the main asteroid belt between Mars and Jupiter, Ceres is the largest unexplored world of the inner Solar System.
It was discovered on January 1, 1801 by the Italian astronomer and monk Giuseppe Piazzi.
For the last century, it was known as the largest asteroid in the Solar System. But in 2006, the International Astronomical Union reclassified it as a dwarf planet because of its large size – Ceres is roughly 950 km in diameter.
Planetary scientists believe Ceres contains rock in its interior with a thick mantle of ice that, if melted, would amount to more fresh water than is present on our planet.
The materials making up Ceres likely date from the first few million years of the Solar System’s existence and accumulated before the planets formed.
NASA’s Dawn robotic spacecraft has become the first mission to achieve orbit around Ceres.
The spacecraft was about 61,000 km from the dwarf planet when it was captured by the planet’s gravity at about 7:39 a.m. EST (4:39 a.m. PST, 12:39 p.m. GMT).
Mission controllers received a signal from Dawn at 8:36 a.m. EST (5:36 a.m. PST, 1:36 p.m. GMT) that the probe was healthy and thrusting with its ion engine, the indicator Dawn had entered orbit as planned.
“We feel exhilarated. We have much to do over the next year and a half, but we are now on station with ample reserves, and a robust plan to obtain our science objectives,” said Dr Chris Russell of the University of California, Los Angeles, principal investigator of the Dawn mission.
In addition to being the first spacecraft to visit a dwarf planet, Dawn also has the distinction of being the first mission to orbit two different worlds in deep space.
The spacecraft has already delivered more than 30,000 images and many insights about 4 Vesta, the second most massive body in the asteroid belt. Dawn orbited Vesta, which has an average diameter of 525 km, from 2011 to 2012.
The most recent images received from the spacecraft, taken on March 1, show Ceres as a crescent, mostly in shadow because the spacecraft’s trajectory put it on a side of Ceres that faces away from the Sun until mid-April.
When Dawn emerges from Ceres’ dark side, it will deliver ever-sharper images as it spirals to lower orbits around the planet.
