Virgin Galactic’s founder, Richard Branson, had initially suggested that he hoped to see a maiden flight by the end of 2009, but this date has been delayed on a number of occasions, most seriously by the October 2014 in-flight loss of SpaceShipTwo VSS Enterprise. Branson stated that Virgin Galactic was “in the best position in the world” to provide rocket-powered, point-to-point 3000 mph air travel on Earth. While Branson suggested, in October 2017, that he could travel to space aboard a SpaceShipTwo within six months, it was not until 13 December 2018 that VSS Unity achieved the project’s first suborbital space flight, reaching an altitude of 82. 7 kilometres (51. 4 mi), officially entering outer space by US standards. The project carried a third person as a passenger in February 2019, when a member of the team sat and floated within the cabin during a flight that reached 89. 9 kilometres (55. 9 mi).
"Ganymede's ocean might be organized like a Dagwood sandwich," commented Dr. Steve Vance in a May 1, 2014 statement. Dr. Vance, of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, went on to explain the weird moon's resemblance to the Blondie cartoon character's famous multi-layered sandwiches. The study, headed by Dr. Vance, provides new theoretical indications for the team's "club sandwich" model, originally proposed in 2013. The research appears in the journal Planetary and Space Science.
Launched as GRAIL A and GRAIL B in September 2011, the probes were renamed Ebb and Flow by schoolchildren in Montana. The probes operated in almost circular orbit near the lunar poles at an altitude of approximately 34 miles, until their mission came to an end in December 2012. The distance between the twin probes altered a bit as they soared over areas of lesser and greater gravity that were caused by visible topological features on the Moon's surface, such as impact craters and mountains--as well as by masses that were secreted beneath the lunar surface.
For those craters smaller than 30 kilometers in diameter, he discovered impacts both increased and decreased porosity in the upper layer of the lunar crust.