As we speak -- or at least, as I speak -- Earth is crossing the path of an unusual comet, and you may be able to see pieces of it for yourself in the next couple days.    Plus, you’ll learn about what’s probably the only NASA mission that you can appropriately celebrate with a mojito, today on SciShow Space News.   [Intro]   If you’ve seen a shooting star -- or more accurately, a meteoroid -- in the last few weeks, chances are it was part of the Delta Aquarids, a meteor shower that will last until the end of August.     Though dimmer than the more famous Perseids, which start next month, these meteoroids are special.  The Delta Aquarids are known for leaving persistent trains -- trails of glowing gas that can last several seconds, even minutes after the meteoroid has faded.     When meteoroids of any sort hit the dense atmosphere of the Earth, friction with air molecules heats up and vaporizes the space rock, leaving behind a glowing streak of gases.  That’s what makes the so-called “shooting star.”   But when a meteoroid hits the atmosphere at supersonic speeds, it can actually ionize the air around it, tearing the electrons from their parent atoms.  As the electrons slowly re-attach to their atoms, they emit light, sometimes for several minutes.   And this might be why the Delta Aquarids leave their trademark persistent trains. But we still don’t know very much about them.   Meteor showers are the result of Earth passing through the rocky debris left behind by a nearby comet.    And the Delta Aquarids correspond with Earth crossing the path of an odd comet known as 96P/Machholz.   It was discovered in 1986, but only during its pass by us in 2007 did astronomers find that it has far less carbon than any other comet or asteroid we know.     Scientists at the Lowell Observatory discovered that it contained 72 times less cyanogen, which is a common carbon-containing molecule, than the average space rock.   And we don’t know why!   Unlike many other comets, which are believed to originate in the suburbs of our solar system -- the Oort Cloud -- astronomers think that 96P might come from even farther outside our system, where carbon may be less abundant.   So on Monday and Tuesday, when the Delta Aquarids peak, you may see the light from burning gas and rock that came to you from very, very far away.   The meteor shower will reach its max around July 28th, with 15 to 20 meteors per hour in the constellation Aquarius.    The best viewing will be in the southern hemisphere and northern tropics, but if you live farther north, you might still be able to seem them zooming around the southern horizon.   And as a bonus, they’ll peak during the new moon, so the sky will be extra dark for your meteoroid-viewing pleasure.     Speaking of the tropics, check out the latest from of one of NASA’s least publicized missions, the NASA Extreme Environment Mission Operation, or NEEMO.   If you’re looking for Bill Murray in that picture, you can stop now. This is part of how astronauts train for the extreme environment of space.     19 meters below the surface of the Atlantic Ocean, 10 kilometers off the coast of Key West, Florida, astronauts from around the world have taken up residence in the remote Aquarius Reef Base, the world’s only undersea research station.   On Monday, a crew of four “aquanauts,” as they’re called, from the US, France, and Japan started NEEMO’s 18th training mission, which will last nine days.   It began with 15 hours of decompression time, which they’ll have to repeat before they resurface.  And now they’re living in a 37-square-meter habitat that mimics the cramped quarters aboard a real spacecraft.   Inside the base, and during 10 trips outside of it, the crew will test will test technology and training techniques for use in the International Space Station, including the first-ever manned drilling operation in low gravity, using a meter-long underwater drill at the end of a 4-meter-long boom.     And all the while, the aquanauts themselves will be subjects of the study into behavioral health and habitability in a confined environment.     So, we wish you well, brave aquanauts! Thanks for doing yet another thing that I myself would never want to do, but I’m glad is being done.   And thank you, person on the other side of the computer, as always for watching SciShow Space News!     If you want to keep exploring the universe with us, check out Subbable.com/SciShow to learn how you can help support us. And don’t forget to go to youtube.com/scishowspace and subscribe!