The Soyuz TMA-18 spacecraft arrived by train to the launch pad at the Baikonur Cosmodrome, Kazakhstan, Wednesday, March, 31, 2010. The launch of the Soyuz spacecraft with Expedition 23 Soyuz Commander Alexander Skvortsov, Flight Engineer Mikhail Kornienko and NASA Flight Engineer Tracy Caldwell Dyson is scheduled for Friday, April 2, 2010 at 12:04 a.m. Eastern. Image Credit: NASA/Bill Ingalls

Subtle color differences on Saturn’s moon Mimas are apparent in this false-color view of Herschel Crater captured by NASA’s Cassini spacecraft during its closest-ever flyby of that moon. The image shows terrain-dependent color variations, particularly the contrast between the bluish materials in and around Herschel Crater and the greenish cast on older, more heavily cratered terrain elsewhere. The origin of the color differences is not yet understood, but may be caused by differences in the surface composition between the two terrains. False color images from Cassini’s previous closest encounter, in 2005, also showed such variations. The natural color of Mimas visible to the human eye may be a uniform gray or yellow color, but this mosaic has been contrast-enhanced and shows differences at other wavelengths of light. During this flyby on Feb. 13, 2010, Cassini came within about 5,900 miles of Mimas and these images were obtained with Cassini’s narrow-angle camera on that day at a distance of approximately 10,000 miles from Mimas. The images were re-projected into an orthographic map projection. A black and white image, taken in visible light with the wide-angle camera, is used to fill in parts of the mosaic. Image Credit: NASA/JPL/Space Science Institute

NASA’s 13-day, STS-131 mission by the shuttle Discovery will mark a couple of spaceflight milestones, the first times four women and two Japanese have been in space at the same time.

Shuttle Discovery is scheduled to lift off from NASA’s Kennedy Space Center on a re-supply mission to the International Space Station on Monday, April 5, at 6:21 a.m., EST.

The shuttle’s seven-member crew includes Mission Specialists Stephanie Wilson, Dottie Metcalf-Lindenburger, and Naoko Yamazaki of the Japan Aerospace Exploration Agency.

Three Expedition 23 space station crew members, including NASA flight engineer Tracy Caldwell Dyson, are scheduled to lift off aboard a Russian spacecraft from the Baikonur Cosmodrome in Kazakhstan on Friday, April 2, at 12:04 a.m., EST, setting the stage for the two milestones.

The space station dockings of the Soyuz crew on Sunday, April 4, at 1:26 a.m, EST, and Discovery on Wednesday, April 7, at 3:50 a.m., EST, will unite 13 U. S., Russian and Japanese astronauts.

The three Expedition 23 crew members, including Soichi Noguchi of the Japan Aerospace Exploration Agency, reached the space station on Dec. 22.

Wilson, 43, who will serve as one of Discovery’s robotics offers, is participating in her third shuttle mission, all launched since NASA’s recovery from the 2003 shuttle Columbia tragedy.

Metcalf-Lindenburger, 34, will be the fourth of NASA’s educator-astronauts, to take flight. The Vancouver, Wash., high school Earth science and astronomy teacher joined NASA’s astronaut corps in 2004. She will serve as Discovery’s flight engineer.

Yamazaki, a 39-year-old aerospace engineer, was selected by JAXA for astronaut training in 1999. The mission marks her first spaceflight. Yamazaki will supervise the cargo transfers between shuttle and space station.

Caldwell Dyson, a 40-year-old chemist, is embarking on a six-month space station voyage. She’ll serve as a flight engineer. Caldwell Dyson flew previously on the STS 118 mission in 2007.

Led by Alan Poindexter, a U. S. Navy Captain, Discovery’s mission will deliver 3,800 pounds of new science equipment and other supplies to the station in the European Space Agency-furnished Multi-Purpose Logistics Module Leonardo.

The new science gear includes the Muscle Atrophy Research and Exercise system rack, or MARES, which will help astronauts exercise seven different joints and attached muscles that weaken during lengthy periods of weightlessness. MARES will enable astronauts to measure changes in muscle mass during their missions for the first time, revealing the effectiveness of exercise regimes intended to slow the deterioration.

The new Window Observational Research Facility, or WORF, will position cameras, spectral scanners, camcorders and other sensors over an optical quality window in the station’s U. S. Destiny science module. The new imagers will enable astronauts to carry out climate change studies, make land and sea observations and detect weather-related crop damage.

Discovery will deliver a third Minus Eighty Laboratory Freezer for ISS, or MELFI, for the preservation of blood, urine and saliva specimens collected as part of crew health studies. Plant and microbial samples will be stored in the freezer as part of experiments assessing the effects on weightlessness on their development.

During three spacewalks, Discovery astronauts Clay Anderson and Rick Mastrachhio will replace an external Ammonia Tank Assembly. The bulky tank holds an ammonia coolant that circulates through the station to remove the heat generated by internal electronics.

Jim Dutton, a U. S. Air Force colonel, will serve as Discovery’s pilot.

Space Station commander Oleg Kotov, flight engineer T. J. Creamer and Noguchi will be joined by Russians Alexander Skvortsov and Mikhail Kornienko as well as Caldwell Dyson as the new Soyuz docks.

Discovery’s will mark NASA’s second shuttle mission of 2010.

NASA’s shuttle fleet is facing retirement after three additional missions

Huntsville, Alabama: April 9th – 10th, 2010

Colorado Springs: April 12th – 15th, 2010