14 DAY TRIAL // The American space agency's MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) space probe is currently orbiting around in the inner solar system, on a course that will set it into Mercury's orbit in early 2011. The probe has just recently completed its third and final flyby of the innermost planet, and managed to send back a number of high-resolution photos of the surface. Among the new data that were transmitted to Earth, astronomers discovered evidence that the last flight above the planet before orbital insertion took place as “seasons” on Mercury changed.
In spite of being so successful, the last flyby was not everything mission controllers had hoped for. A data glitch, that occurred as the spacecraft was moving away from the planet, meant that only half of the ground and atmospheric observations it made got relayed back to NASA. Still, a wealth of images showing previously-unobserved areas became available. Over all three flybys, the goal has been to provide the highest level of coverage possible. The way this was accomplished was by splitting the surface of Mercury into sectors, and then photographing each of them during a flight.
In the last instance, the $446 million probe flew only about 142 miles (228 kilometers) above the surface, which allowed it to snap some pretty high-detail images of various targets. During all three approaches, MESSENGER looked at exospheric concentrations of sodium, calcium and magnesium, three main types of atoms on Mercury. The latest readings showed significantly lower levels of sodium than those recorded during the first flyby. “While this is dramatic, it isn't totally unexpected,” Johns Hopkins University (JHU) Applied Physics Laboratory (APL) mission scientist Ronald Vervack, Jr. said.
The planet does not have an atmosphere per se, but rather a loose concentration of various chemical elements, whose molecules do not collide or adhere to each other. The planetary “coating” is similar to the one found on the Moon. Another observation was of a double-impact basin, that is similar to another one on Mercury, called Raditladi.
“One similarity to Raditladi is its age, which has been estimated to be approximately one billion years old. Such an age is quite young for an impact basin, because most basins are about four times older. The inner floor of this basin is even younger than the basin itself and differs in color from its surroundings. We may have found the youngest volcanic material on Mercury,” Arizona State University imaging team member and postdoctoral research Brett Denevi said, quoted by Space.