Looks like Odyssey may have found caves on Mars.
The description seems quite different from caves one finds on Earth (these caves are on Mars, after all), sounding more like sinkholes. Being at high altitudes on Arsia Mons and 300-800ft across, they’re probably too remote and too large to use for early settlements.
When the NASA anounced the discovery of caves on Mars, I was very excited. So I decided to look for other pictures of the same place, and I found that what looked like caves were in fact only sinkholes like it’s said in the article.
You can see the pictures and more on my blog : http://marsblog-grottes1.2-www.de