Study Suggests Mercury May Have Shrunk About 30 Percent More Than Expected
A study in Geophysical Research Letters estimates Mercury may have contracted roughly 30 percent more than earlier calculations, losing as much as 14 miles in diameter. The BepiColombo mission, due to enter orbit in November, should test the figure with its laser instrument.
The findings appear in the journal Geophysical Research Letters. According to the report, that loss is significant for a planet barely 3,000 miles (4,900 kilometers) across.
Researchers say Mercury's rough surface, continually reshaped by debris hurled from impact craters, may have hidden the true extent of the shrinkage from earlier measurements.
Gaku Nishiyama, the study's lead author, who is taking part in a mission to Mercury, said the BepiColombo spacecraft's laser instrument should confirm how much the planet is withering as a result of internal cooling. He also said the shrinkage could be even more than his team is estimating from measurements taken by NASA's Messenger spacecraft in the 2010s.
The news comes one week after a pair of European and Japanese spacecraft shed its cruising platform and advanced toward Mercury. The linked craft, known as BepiColombo, are expected to enter orbit around Mercury in November before splitting up for a fuller survey.
Only one other spacecraft has ever visited Mercury, NASA's Mariner 10, in the 1970s.