Former Florida senator Bill Nelson was sworn in Monday as head of NASA, hailing a "new day" for space exploration as the United States seeks to return to the Moon.

With his hand on a Bible, Nelson took the oath of office from Vice President Kamala Harris as he officially took up the role of NASA administrator.

"It's a new day in space," he said, after bringing a Moon rock to the event.

Nelson, 78, who traveled into space in 1986, takes over the agency with the United States hoping to put astronauts back on the Moon by 2024.

Humans last set foot on the Moon in 1972 during the Apollo program.

Under the Artemis program, NASA wants to establish a sustainable presence, complete with a lunar space station, to test new technologies that would pave the way for a crewed mission to Mars.

The interaction of two doomed stars has created this spectacular ring adorned with bright clumps of gas—a diamond necklace of cosmic proportions. Fittingly known as the "Necklace Nebula," this planetary nebula is located 15,000 light-years away from Earth in the small, dim constellation of Sagitta (the Arrow).

A pair of tightly orbiting sun-like stars produced the Necklace Nebula, which also goes by the less glamorous name of PN G054.203.4. Roughly 10,000 years ago, one of the aging stars expanded and engulfed its smaller companion, creating something astronomers call a "common envelope." The smaller star continued to orbit inside its larger companion, increasing the bloated giant's rotation rate until large parts of it spun outwards into space. This escaping ring of debris formed the Necklace Nebula, with particularly dense clumps of gas forming the bright "diamonds" around the ring.

The pair of stars which created the Necklace Nebula remain so close together—separated by only several million miles—that they appear as a single bright dot in the center of this image.

An icy satellite of Saturn, Enceladus, has been a subject of increasing interest in recent years since Cassini captured jets of water and other material being ejected out of the south pole of the moon. One particularly tantalizing hypothesis supported by the sample composition is that there might be life in the oceans under the ice shells of Enceladus. To evaluate Enceladus' habitability and to figure out the best way to probe this icy moon, scientists need to better understand the chemical composition and dynamics of Enceladus' ocean.

Specifically, an appropriate salinity could be important for habitability. Like the porridge of the Three Bears, the salt level of the water must be just right for life to thrive. Too high a salinity could be threatening to life, and too low a salinity may indicate a weak water-rock reaction, limiting the amount of energy available to life.

By Earth standards, the surface of Mars is the picture of desolation. It's not only irradiated and cold enough to make Antarctica look balmy, but it's also one-thousands times drier than the driest places on Earth. However, beneath the super-arid surface of the Red Planet, there are abundant supplies of water ice that could someday be accessible to human explorers (and even settlers).

This is especially the case in the mid-latitude region known as Arcadia Planitia, a smooth plain located in Martian northern lowlands. According to new research conducted with support from NASA's Jet Propulsion Laboratory (JPL), the region shows signs of glaciers and glacier activity. These findings could prove very useful for the future human landings and exploration of Mars, not to mention potential settlement.

The study, which recently appeared in the scientific journal Icarus, was led by Shannon Hibbard—a Ph.D. candidate in geology and planetary science at the University of Western Ontario (UWO). She was joined by Dr. Gordon R. Osinski of UWO's Institute for Earth and Space Exploration (IESE), and Etienne Godin, a data scientist at the Center for Northern Studies at Laval University; and Nathan Williams and Matthew Golombek of NASA JPL.