John N. Bahcall (BS 1956) worked on the Standard Solar Model and the Hubble Space Telescope, resulting in a National Medal of Science. Peter Smith (BS 1969) was the principal investigator and project leader for the NASA robotic explorer "Phoenix", which physically confirmed the presence of water on the planet Mars for the first time. Astronauts James van Hoften (BS 1966), Margaret Rhea Seddon (BA 1970), Leroy Chiao (BS 1983), and Rex Walheim (BS 1984) have orbited the earth in NASA's fleet of space shuttles.