December 9, 2013 | Sol 477

Land O'Lake: I found evidence for an ancient freshwater lake on Mars. Details: http://t.co/Ide83zfOgZ pic.twitter.com/FvcOC1Drom — Curiosity Rover (@MarsCuriosity) December 9, 2013

Beyond Cooperstown

At a meeting on Earth, my scientists are reporting a bunch of results from my Yellowknife Bay studies. By comparing John Klein to other rocks, they found that not only did freshwater flow in streams across the surface, it probably also ponded up as a huge lake. I’m glad I don’t have to try swimming across something like that.

Another rock I drilled, called Cumberland, turns out to date between 3.86 billion and 4.56 billion years old. This is about the range scientists were expecting, but it’s the first time anyone has managed to measure the exposure age of a rock on the surface of another planet. Another first for me. I did it by measuring how much potassium was in the rock compared with argon, which it radioactively decays to over time.