Great valley larger than Grand Canyon discovered on Mercury Pluto’s heart hides ocean

Washington: Scientists have discovered a 400 kilometres wide “great valley” in the southern hemisphere of Mercury which provides more evidence that the small planet closest to the Sun is shrinking.

Scientists used stereo images from Nasa’s Messenger spacecraft to create a high-resolution topo map that showed the broad valley — more than 1,000 kilometres long extending into the Rembrandt basin, one of the largest and youngest impact basins on Mercury.

About 400 kms wide and three kilometres deep, Mercury’s great valley is smaller than Mars’ Valles Marineris, but larger than North America’s Grand Canyon and wider and deeper than the Great Rift Valley in East Africa.

“Unlike Earth’s Great Rift Valley, Mercury’s great valley is not caused by the pulling apart of lithospheric plates due to plate tectonics; it is the result of the global contraction of a shrinking one-plate planet,” said Tom Watters, senior scientist at the Smithsonian National Air and Space Museum, in US.

Mercury’s great valley is bound by two large fault scarps — cliff-like landforms that resemble stair steps. The scarps formed as Mercury’s interior cooled; the planet’s shrinking was accommodated by the crustal rocks. Los Angeles: Pluto may harbour a vast liquid ocean lying deep beneath the icy dwarf planet’s frozen heart, according to an analysis of features unveiled by New Horizons spacecraft.

The idea that Pluto has a subsurface ocean is not new, but the study provides the most detailed investigation yet of its likely role in the evolution of key features such as the vast, lowlying plain known as Sputnik Planitia.

It forms one side of the famous heart-shaped feature seen in the first New Horizons images, is suspiciously well aligned with Pluto’s tidal axis. The likelihood that this is just a coincidence is only five per cent; alignment suggests extra mass interacted with tidal forces between Pluto and its moon Charon.