The NASA Dawn spacecraft is about to make its second and last stop on its journey to the asteroid belt and is already sending some awesome photos that leave more questions than answers.
After parting with the asteroids Vesta in 2012, Dawn began traveling through an asteroid belt, which occupies the area between the orbits of Mars and Jupiter, to meet with the dwarf planet Ceres. Thus, Dawn will be the first spacecraft to enter the orbit of two celestial bodies during its mission.
The probe will be captured by the gravity of Ceres on Friday, March 6, and, on the eve of this long-awaited event, the probe sends to Earth more and more detailed photos of the inner dwarf planet of the Solar System, which has already puzzled scientists. One of these puzzles is a bright spot on the surface of Ceres, located in the center of the crater.
Speaking at a press conference on Monday at NASA's Jet Propulsion Laboratory in Pasadena, California, Project Deputy Rassvet Carol Raymond outlined some of the reasons that can explain these strange phenomena. As previously reported, one of the possible mechanisms that could form such bright spots is cryovolcanism, passing under the ice surface. But the photos of Dawn are becoming more and more detailed every day, and this hypothesis is becoming less and less likely. We will have to wait until the spacecraft completes its first orbit (at the end of April), during which Dawn's instruments can better calibrate the data.
Although cryovolcanism is becoming less and less likely, the secret of the water of Ceres is one of the most exciting.
"One of the secrets of Ceres is liquid water," said the director of the mission, Dawn and chief engineer Mark Reiman. "Do underground oceans or lakes exist? I think it will be very interesting."
Thanks to observations and theoretical models, scientists have a pretty good idea that Ceres was formed at the beginning of the solar system era. It consists of a layered material with different densities. In addition, there are signs of the presence of underground reservoirs.
Since Ceres does not receive gravitational heat, such as the satellite of Saturn Enceladus or the satellite of Jupiter Europe, sunlight is the only source of heat. Thus, it can be assumed that if Ceres ever had underground reservoirs, then they, most likely, have long been frozen.
Waiting for Dawn to see Ceres covered with ice strengthened last year, when the ESA Herschel Space Telescope discovered water vapor in close proximity to Ceres. Although it was not so large, scientists hoped that this could be a sign of liquid water escaping from underground reservoirs, by analogy with the impressive geysers at the south pole of Enceladus. Another theory is that Herschel accidentally noticed the effect of a meteorite impact on Ceres, which raised surface ice into space. Before the start of the mission Dawn, it was assumed that Ceres could have much in common with Enceladus and Europe - two ice worlds that have underground oceans. But as it turned out, Ceres has an ancient surface covered with craters, unlike the ice crusts of Enceladus and Europe.
But Dawn's instruments are not designed to search for geysers on the surface of a dwarf planet. However, using an infrared spectrometer, the spacecraft is able to detect scattered light formed by dust, which, together with water vapor, is ejected into open space. According to Raymond, Ceres may also have a thin atmosphere.
Instead of meeting some questions as we approach the dwarf planet, Dawn provides us with more and more questions.
“So what can Ceres show us? This is a whole mysterious world that for two centuries looked only like a faint speck of light,” Raymond added. "Now we are finally close to her, and she will reveal her secrets to us."
Video provided by NASA: