U.S. science probe nears unexplored dwarf planet Ceres

05.03.2015 14:58

science satellite on Friday will wrap up a
7-1/2-year journey to Ceres, an unexplored
dwarf planet in the main asteroid belt
between Mars and Jupiter, scientists said on
The Dawn spacecraft visited the asteroid
Vesta before firing its electric ion engine to
continue on to Ceres, a round, 600-mile-wide
(970 km-wide) mini-planet that is the largest
body in the asteroid belt.
Earth’s moon, by comparison, is about 2,160
miles (3,480 km) in diameter.
The solar-powered probe is expected to put
itself into orbit around Ceres at 7:20 a.m. EST
(1220 GMT) on Friday. However, radio
telescopes on Earth will not be in position to
pick up Dawn’s signal until later in the day,
National Aeronautics and Space
Administration officials said at a news
“The approach has gone flawlessly so far,”
said Dawn Project Manager Robert Mase of
NASA’s Jet Propulsion Laboratory in Pasadena,
Scientists are eager for their first close-up
look at a dwarf planet, believed to be a
building block left over from the formation of
the planets 4.6 billion years ago. “They’re
literally fossils that we can investigate to
understand the processes that were going on
at that time," said Dawn scientist Carol
Raymond, also with Jet Propulsion Laboratory.
Another NASA spacecraft, New Horizons, will
fly by the distant dwarf planet Pluto in July.
Pluto, once considered one of the planets of
the solar system, was later downgraded to a
dwarf planet.
Ceres, namesake of the Roman goddess of
agriculture, is already providing intrigue.
Pictures relayed from Dawn last month show
bright streaks on its surface, including two
very bright spots inside a crater. “These spots
were extremely surprising,” Raymond said.
Scientists suspect Ceres may have had an
underground ocean early in its history that
later froze. Impacting asteroids or comets
could then have exposed patches of highly
reflective ice.
Europe’s Herschel space-based telescope
previously detected water vapor on Ceres, a
clue that impacting bodies may periodically
send plumes of watery material shooting into
space. “In the initial views of Ceres, we see
many strange features: smooth areas, areas
that chaotically fractured and craters of all
shapes and sizes,” Raymond said. “Of
particular interest are the bright spots ...
which stand out against Ceres' dark surface.”
It will take Dawn about a month to position
itself for 14 months of observations of Ceres.
In all, the mission is costing NASA $473