Kathy Sullivan, from Shuttle Challenger to the Challenger Deep

Space travel is a great achievement for anyone, given the selection process and training that astronauts must excel in.  Astronauts belong to a very exclusive club of explorers, but there's one club even more exclusive: ocean explorers who have gone to the greatest depth of the seas, to the bottom of the Challenger Deep.  Until this week, there were only seven members in that club. It's been expanded now to eight, and Number 8 is a big deal.  
Dr. Kathryn Sullivan has now become a member of both clubs. That puts her in a new club, with a memebership of exactly one person.
Sullivan spacewalked outside the space shuttle Challenger in 1984 on one of her three trips to orbit, becoming the first American woman to do an EVA. On STS-31 in 1990, she helped deploy the Hubble Space Telescope. Just another day at the office for Sullivan, who went on to be Payload Commander for STS-45, a Spacelab mission focused on Earth science. 
She moved on to other achievements, including heading the National Oceanic and Atmospheric  Administration (NOAA). 
Now, in a submersible called the Limiting Factor, from a host ship named Pressure Drop (why should Elon Musk have all the fun with odd names?) as part of an exploration effort by a group called Caladan Ocean, she and pilot/submersible builder Victor Vescovo (who'd been there once before) touched the bottom of the sea. 
Sullivan had pre-NASA submersible experience, having studied fault zones off California and the Mid-Atlantic Ridge among other targets, but had never been near this depth.  She wrote on Facebook that the depth gauge read 10,915 meters or 38,810 feet.  That's a fun number for me to think about because I used to run 10K races.  It's hard to believe humans can go that far down, where pressure is over a thousand times what it is at sea level and very, very few creatures can live. It's a voyage so - well, challenging - that the first visit by a craft carrying humans was made in 1960 and there was no second trip until James Cameron did it in 2012. 
One more bit of symmetry: the Challenger Deep is named for the British exploration vessel Challenger, which discovered it, and the shuttle was named after the ship.
It bears repeating that Sullivan, who was an oceanographer and geologist before she shifted gears to become an astronaut, is the only human being, man or woman, to have been to that height (~600 km) and that depth.  While astronauts have trained in underwater facilities, and Scott Carpenter of the Mercury program became an aquanaut, Sullivan went "below and beyond" and will have this "first" forever. 

Sullivan in her astronaut days (NASA)

Sullivan in one of her natural habitats, space, on STS-31 (NASA)

Oh, and she has a new book! I'll review it soon.

I don't know what she will do to top this (go to Mars, perhaps?), but based on her life so far, she's likely to push more new frontiers.