Icy Twin Craters on Mars

Contributed by
Mar 10, 2015, 1:00 PM EDT

I’ve mentioned a few times here that I write a biweekly column for, a site that has lots of news and blogs dealing with space exploration (Sen stands for “Space Exploration Network”). The news articles are free, but the blogs are subscription only.

My latest article there is one I’ve been meaning to write for some time: What phenomenon sculpted this weird pair of craters, each with a central pit in it? It turns out the answer is … layered. is worth the subscription price. There are a lot of good writers there, including my friends Emily Lakdawalla, Chris Lintott, and many more. Go check it out!