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Dawn Spacecraft Sends First Color Images of Ceres

Red and blue tell the tale of a dwarf planet covered in rock and ice

A false-color image of Ceres mimics what human eyes would see (NASA/JPL-Caltec/UCLA)
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Ever since NASA’s Dawn spacecraft arrived in orbit around the dwarf planet Ceres in early March, scientists have been eagerly awaiting a flood of data that will hopefully tell researchers more about the origin of the solar system. Now, the team has created the first color photographs of the largest body swinging through space in the asteroid belt between Mars and Jupiter.

For the last month, news from Dawn has been quiet as the spacecraft gently spirals closer Ceres, hidden in the dark side of the dwarf planet. This is, as Robbie Gonzalez at io9.com explains, not because we are trying to sneak up on aliens:

The lack of photos obviously has absolutely nothing to do with the fact that the Dawn spacecraft is currently orbiting over Ceres' far-side, i.e. the side facing away from the sun, i.e. the side that is, at this very moment, completely shrouded in darkness and otherwise unphotographable. Nope. That's not it at all.

Earlier this month the probe captured some images, compiled in this video, of sunlight illuminating the north pole. Now, to tide people over until the dwarf planet’s next photoshoot, scientists have rendered Ceres in color. NASA’s Jet Propulsion Laboratory put together a colorized map of the planetary surface. A press statement explains how Dawn 'sees’ color:

Images taken using blue (440 nanometers), green (550 nanometers) and infrared (920 nanometers) spectral filters were combined to create the map. The filters were assigned to color channels in reverse order, compared to natural color; in other words, the short-wavelength blue images were assigned to the red color channel and the long-wavelength infrared images are assigned to the blue color channel.

At The Conversation, David Rothery, a planetary geoscientist, writes that the resulting map — which looks as pock-marked and pebbly as a cartoon dinosaur’s skin — approximates what human eyes would see. Likely, the blue splotches are ice and the red areas are relatively bare and rocky. The patchiness of the surface colors tell the researchers that Ceres was once an active body. Geological processes must have painted its surface with multiple, diverse regions, the NASA report explains.

Even those ruddy areas may just cover ice underneath. As far as researchers can tell, a quarter of the dwarf planet’s outer portion is ice and the inside is rocky. But they still have questions. Rothery writes:

Is Ceres’ icy shell solid all the way down to the rock, or have lower layers of the ice melted to produce the sort of internal ocean known to exist within some of the icy satellites of Jupiter (Europa) and Saturn (Enceladus)? If there is an internal ocean, this could account for plumes of water vapor seen venting from Ceres last year by the Herschel space telescope – not to mention those mysterious white spots seen on the Ceres' surface.

And another unanswered question has to do with a set of mysteroius white spots that gleamed like beacons shining from a crater captured earlier this year. Despite the new images, these glowing dots still offer a tantalizing mystery. "The bright spots continue to fascinate the science team, but we will have to wait until we get closer and are able to resolve them before we can determine their source," says Chris Russell, of the University of California, Los Angeles, in a press statement from NASA

Dawn will start its first detailed, intensive survey of Ceres on April 23, when it reaches 8,400 miles above the dwarf planet’s surface.

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