Using data from the spacecraft Messenger Paul Byrne and his colleagues from Carnegie Institution for Science, Washington, U.S., calculated the speed of Mercury shrinkage and stated that the planet closest to the Sun was contacting at a rate 2 to 8 times greater than computer models and former probes had shown.
In comparison with the Earth’s surface, the outer shell of Mercury, named lithosphere, consists of a single tectonic plate, not of several ones. In order to estimate the shrinkage, the researchers studied Mercury’s tectonic features, the so-called lobate scarps and ridges which emerged as a result of the planet’s cooling and contracting. During the investigation they used images which the spacecraft Messenger had collected since its entry into Mercury’s orbit in 2011.
After analyzing the shape of these structures, their disposition and depth specialists have found out that over the recent 4 billion years Mercury has lost as much as 5-7 km in radius instead of 0.8 —3 km as it was estimated earlier. Thus it was found out that Mercury was shrinking at a rate 2 to 8 times greater than Mariner-10 and computer models had observed. The reason for this fast shrinking is still unknown to scientists.