Here are this week’s Twitter #weirdscifacts! Due to a death in the family, I was traveling and had a difficult time finding facts on some days, but thankfully others stepped in to help me out, and we have two for September 2nd!

536. Aug 31: Bizarre fish evolved for the oceans, but lives on land! 

537. Sep 01: Fire tornadoes — enough said.  (h/t @discoveryplace)

538. Sep 02: The echidna has a four-pronged penis; it uses two prongs each mating, and swaps sets between matings. (via @larwe, who added: “You might call it the original Swiss Army Penis.”)  The link contains perhaps an even more bizarre revelation: the sperm of the echidna will work together to reach their target, traveling in groups!  Because a female can be inseminated by multiple sperm at once, it is an evolutionary benefit for the sperm to work together.  I imagine it somewhat like bicyclists in the Tour de France drafting off of one another!

538a. This rare genetic disorder, caused by intense inbreeding, is known as Polygamist’s Downs.  (via @stevesilberman)

539. Sep 03: A felt-tipped marker helped the Apollo 11 astronauts leave the moon & get home.  (This is number 8 on list of “myths” about the moon landing.  This story is true, though it was modified to promote the “space pen”.)

540. Sep 04: Valles Marineris canyon system of Mars — 8x longer, 10x wider & 4x deeper than the Grand Canyon.  Thanks in part to the lower gravity, everything is bigger on Mars!  We’ll see more examples of this in future posts.  Keep in mind that, roughly speaking, 320 Grand Canyons could fit in this Martian canyon system.

541. Sep 05: c. 1930, a volcanologist Frank Perret survives in the path of a pyroclastic flow.  I’ve known about this story for a long time, but couldn’t remember the details! (and a Google search didn’t find it!)  A pyroclastic flow from the same mountain killed some 30,000 people in the city of St. Pierre years earlier — Perret was extraordinarily lucky.

542. Sep 06: Project Mohole, the 1960 attempt to drill through the Earth’s crust to the Mantle!  Though the project didn’t succeed, give this some thought — they were trying to drill into the molten region of the Earth!  It was still an impressive technological achievement that brought back much useful scientific data.