Planet Mercury Has Shrunk More Than Thought

sciencehabit writes "Measuring just 4880 kilometers across, Mercury is a small world. The planet became slightly smaller as its interior cooled, which caused Mercury to shrink, buckling its surface and creating numerous cliffs and ridges. Now, after studying 5934 of these features, researchers report online today in Nature Geoscience that Mercury's contraction was much greater than previously thought: During the past 4 billion years, the planet's diameter decreased by 7 to 14 kilometers. The greater estimate of shrinkage accords with models that predict how much a rocky planet should contract as its interior cools; the new work may also lend insight into the evolution of extrasolar planets that, like Mercury and unlike Earth, lack any moving continents."

Re:Laugh

[Shakrai]

I'm surprised to hear it has "cooled" with it's greatest distance from the Sun being a mere 69,816,900 km.

The dark side of Mercury is a balmy -280F. Hard to retain any meaningful amount of heat when you have no atmosphere. :)

Re:Whoa, tiny planet!!

[Hussam Al-Tayeb]

nope, decreased by 14km (not TO 14km). It i still around twice the size of pluto.

Re:Whoa, tiny planet!!

[sidyan]

Mercury [wikipedia.org]'s diameter is 2.11 times that of 134340 Pluto [wikipedia.org], but its mass is 25.3 that of the puny dwarf planet.

Discounting metallic hydrogen on Jupiter and Saturn, Mercury's definately the most Metal planet in the solar system.

Re:Laugh

[Anonymous Coward]

Lets turn this around, how would an atmosphere promote loss? Where does that heat go? It still has to deal with vacuum insulation, just now a few kilometers higher than before. You can have evaporative cooling of some sort, where heat blows off part of the atmosphere, but then it wouldn't last very long without a source on the surface. Otherwise, it would help trap heat, which still has to go into the vacuum of space to fully leave the planet.