Yesterday, March 6, at about 12:39 pm GMT, the NASA probe Dawn arrived at Ceres, becoming the first spacecraft to go into orbit around a dwarf planet. Observations of Dawn over the next 16 months should lift the veil over Ceres, which has attracted the attention of scientists since its discovery in 1801.
"Since its discovery in 1801, Ceres has been known as a planet, then as an asteroid, and now as a dwarf planet," said the head engineer of the mission, Rassvet Marc Ryman from the NASA Jet Propulsion Laboratory in Pasadena, California. "Now, after a journey of 3100000000 miles (4, 9 billion km) and 7, 5 years, Rassvet can call Ceres his home."
Officials from NASA received a signal from Dawn, confirming that it is in perfect order and went into orbit at 13:36 GMT.
This event happened four months before the meeting with another dwarf planet: July 14, NASA's New Horizons probe will approach the Pluto system, giving scientists the first good photos of a distant dwarf planet and its five famous satellites.
Dawn of the Solar System
Spacecraft Rassvet worth $ 473 million was launched in September 2007 to explore Vesta and Ceres, the two largest objects in the main asteroid belt between Mars and Jupiter. The diameter of Vesta is 330 miles (530 kilometers), while Ceres is about 590 miles (950 km) wide. Vesta and Ceres keep the prints of the very first days of the Solar System and are protoplanets that would most likely continue to grow if it were not for the effects of Jupiter’s huge gravity.
"The two bodies are intact protoplanets of the earliest solar system," says Deputy Chief Explorer of the Dawn Mission, Carol Raymond. "So they literally are fossils that we can explore to understand the processes that were going on at the time."
Dawn was in the orbit of Vesta from July 2011 to September 2012, after which the probe went to Ceres. Thus, today's event can be viewed from a different point of view: Dawn became the first spacecraft to go into orbit of two objects outside the Earth-Moon system.
The mission’s space exploit was made possible thanks to the Dawn's innovative engine system, which accelerates xenon ions from the back of the ship. This process generates a small amount of thrust. Dawn takes four days to pick up speed from 0 to 60 miles per hour (97 km / h).
But the Dawn ion engine is about 10 times more efficient than traditional chemical systems. Thus, the engines can continue to work for weeks, months or even years, accelerating the Dawn to enormous speeds.
"1000 pounds of xenon rocket fuel that was loaded aboard the Dawn, has already allowed to reach speeds of 24,000 miles per hour," said project leader Rassvet Robert Mace at a press conference on Monday. Thanks to the ionic engines, Dawn crept up to Ceres slowly and gradually. The probe quietly went into orbit without any heavy maneuvers.
Secrets of Ceres
Ceres is an intriguing world that is in many ways more similar to the icy satellites of the outer part of the Solar System, such as Jupiter’s Europa and Saturn’s Enceladus, than to its rocky neighbors in the asteroid belt.
For example, Ceres, as scientists believe, consists of 25-30% of water, which is present in the form of ice. The dwarf planet may also have once had, and perhaps now has, a liquid ocean beneath the surface, like Europe or Enceladus. Some researchers believe that Ceres may be able to maintain a microscopic life.
"It will be really interesting to see what this alien world looks like," said Reiman.
Dawn is not equipped with special tools to search for life, but the probe is able to detect evidence of the subterranean ocean (if it really exists). Measuring the surface temperature of Ceres in combination with the heat distribution models for Ceres can also shed light on the question of underground liquid water.
Dawn also investigates the two secrets of Ceres, which were discovered about two years ago. Scientists will try to find out the nature of the mysterious bright spots on the surface and the weak jet of water vapor that was noticed by the Herschel European Space Observatory. In general, Dawn will examine the dwarf planet in detail, examining its surface and determining what Ceres is made of.
This work will not begin immediately. Dawn will spend the next six weeks, gradually approaching the required orbit, to which the probe will be released on April 23, and after that will begin to explore Ceres from an altitude of 8400 miles (13,500 km).
Summarizing
Although Ceres and Pluto are dwarf planets, they are very different from each other.
"Pluto was formed differently, at another time, and from another material," said Russell.
Pluto is also more than twice as large as Ceres and lies 14 times farther than the Sun. Thus, the data returned by the Dawn probe and the New Horizons spacecraft will most likely not show the big picture.
