(There are caves in Mars!)

1) On The Void. There's an “enormous hole in the Universe, nearly a billion light-years across, empty of both normal matter such as stars, galaxies, and gas, and the mysterious, unseen 'dark matter.'”

2) On the universe, again, or at least half of it. It's the landscape architecture of the cosmos in stunningly huge and beautiful images. (Cf. Filaments of space-time.)

3) On crowd quakes. (Via.)

4) On dark tourism. On sale: The Rough Guide to the Slave Trade, Fodor's Auschwitz and The Lonely Planet Guide to Trench Warfare. (See also Happy Trails and KGB Hotel.)

5) On college campuses, side-by-side cartographic comparisons.

6) On obelisks. There are “21 ancient obelisks still standing” and only 4 are located in Egypt. So where are the others?

(Image credit: NASA/JPL-Caltech/ASU/USGS.)