Previous photogeology estimates of how much Mercury shrunk after formation are revised from a pipsqueak 0.8 to 3 km, to a massive 7 km shrinkfest. Pretty cool that we can figure out shrinkage-rates from planet-wide fault patterns!

Read more on Mercury's time-dependent size the BBC, or hit up the source article on Nature Geoscience. For more Mercury-goodness, remember you can explore the planet using MESSENGER data in Google Earth!

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Thanks to Sparrowgrass & Pitchblende for the tip. Image credit NASA & the MESSENGER mission.