Flight Engineer Thomas Pesquet of ESA is seen floating outside the International Space Station during a spacewalk. Pesquet and Expedition 50 Commander Shane Kimbrough of NASA conducted the six-hour-and-34-minute spacewalk on March 24, 2017. A second spacewalk, by Kimbrough and NASA astronaut Peggy Whitson, is scheduled for Thursday, March 30. http://www.nasa.gov/sites/default/files/thumbnails/image/33531796282_85801ec9ef_o.jpg

The mound in the center of this Mars Reconnaissance Orbiter image appears to have blocked the path of the dunes as they marched south (north is to the left in this image) across the scene. Smaller dunes run perpendicular to some of the larger-scale dunes, probably indicating a shift in wind directions in this area. http://www.nasa.gov/sites/default/files/thumbnails/image/pia21572.jpg

The Pressurized Mating Adapter-3 (PMA-3) is in the grip of the International Space Station's Canadarm2 robotic arm during its relocation and attachment to the station's Harmony module on March 26,2017. A spacewalk by NASA astronauts Shane Kimbrough and Peggy Whitson, which began at 7:29 a.m., will finalize the PMA-3 cable connections on Harmony. http://www.nasa.gov/sites/default/files/thumbnails/image/iss050e060267.jpg

Dr. Nancy Grace Roman is shown with a model of the Orbiting Solar Observatory (OSO) in 1962. She was the first Chief of Astronomy in the Office of Space Science at NASA Headquarters and the first woman to hold an executive position at NASA. She had oversight for the planning and development of programs including the Hubble Space Telescope. http://www.nasa.gov/sites/default/files/thumbnails/image/7538840276_f987be0cb7_o.jpg

Although only a sliver of Saturn's sunlit face is visible in this view, the mighty gas giant planet still dominates the view. http://www.nasa.gov/sites/default/files/thumbnails/image/pia20530.jpg

This illustration shows NASA's Cassini spacecraft about to make one of its dives between Saturn and its innermost rings as part of the mission's grand finale. Cassini will make 22 orbits that swoop between the rings and the planet before ending its mission on Sept. 15, 2017, with a final plunge into Saturn. http://www.nasa.gov/sites/default/files/thumbnails/image/pia21439.jpg

A horse drawn caisson carries former astronaut and U.S. Senator John Glenn to his final resting place during the interment ceremony at Arlington National Cemetery on Thursday, April 6, 2017, in Virginia. Glenn was the first American to orbit Earth on Feb. 20, 1962, in a five-hour flight aboard the Friendship 7 spacecraft. http://www.nasa.gov/sites/default/files/thumbnails/image/33878889975_d79379ae7f_o.jpg

This image, taken by the JunoCam imager on NASA’s Juno spacecraft, highlights a feature on Jupiter where multiple atmospheric conditions appear to collide. http://www.nasa.gov/sites/default/files/thumbnails/image/pia21338.png

The Soyuz MS-02 spacecraft is seen as it lands with Expedition 50 Commander Shane Kimbrough of NASA and Flight Engineers Sergey Ryzhikov and Andrey Borisenko of Roscosmos near the town of Zhezkazgan, Kazakhstan on Monday, April 10, 2017 (Kazakh time). http://www.nasa.gov/sites/default/files/thumbnails/image/33110046934_8e3808871c_o.jpg

Through NASA's Space Technology Research Fellowship (NSTRF) program, a fresh approach to designing and manufacturing heat-thwarting thermal protection systems - or heatshields - for spacecraft is being developed and tested, offering the promise of fabricating larger tile sizes while reducing labor, cost and waste. http://www.nasa.gov/sites/default/files/thumbnails/image/strg_nstrf_edl_visualization_joe_brock2_0.jpg

NASA scientists are releasing new global maps of Earth at night, providing the clearest yet composite view of the patterns of human settlement across our planet. This composite image, one of three new full-hemisphere views, provides a view of the Americas at night. http://www.nasa.gov/sites/default/files/thumbnails/image/blackmarble_2016_americas_composite.png

Starburst galaxies contain regions where stars are forming at such a breakneck rate that the galaxy is eating up its gas supply faster than it can be replenished. http://www.nasa.gov/sites/default/files/thumbnails/image/potw1715a.jpg

When imaged at infrared wavelengths that pierce the planet’s upper haze layer, the high-speed winds of Saturn's atmosphere produce watercolor-like patterns. http://www.nasa.gov/sites/default/files/thumbnails/image/pia20528-1041.jpg

The Orbital ATK Cygnus pressurized cargo module is carried atop the United Launch Alliance Atlas V rocket from Space Launch Complex 41 at Cape Canaveral Air Force Station. Orbital ATK's seventh commercial resupply services mission will deliver 7,600 pounds of supplies, equipment and scientific research materials to the International Space Station. http://www.nasa.gov/sites/default/files/thumbnails/image/33740085360_2b2f52cfe9_o.jpg

At the center of the Centaurus galaxy cluster, there is a large elliptical galaxy called NGC 4696. Deeper still, there is a supermassive black hole buried within the core of this galaxy. New data from NASA’s Chandra X-ray Observatory and other telescopes has revealed details about this giant black hole. http://www.nasa.gov/sites/default/files/thumbnails/image/cen_multi.jpg

The Soyuz MS-04 rocket launches from the Baikonur Cosmodrome in Kazakhstan on Thursday, April 20, 2017 at 1:13 p.m. Baikonur time carrying NASA astronaut Jack Fischer and cosmonaut Fyodor Yurchikhin of the Russian space agency Roscosmos into orbit to begin their four and a half month mission on the International Space Station. http://www.nasa.gov/sites/default/files/thumbnails/image/33771308020_0abc3563f9_o.jpg

NASA's fleet of 18 Earth science missions in space, supported by aircraft, ships and ground observations, measure aspects of the environment that touch the lives of every person around the world. This visualization shows the NASA fleet in 2017. http://www.nasa.gov/sites/default/files/thumbnails/image/final_earth_obs_fleet06hw.2100_1920x1080.jpg

534 days, 2 hours, 49 minutes and counting. NASA astronaut Peggy Whitson flew through the standing record for cumulative time spent in space by a U.S. astronaut at 1:27 a.m. EDT on April 24, 2017, and with the recent extension of her stay at the International Space Station, she has five months to rack up a new one. http://www.nasa.gov/sites/default/files/thumbnails/image/iss050e014337.jpg

It's springtime and the deployed primary mirror of NASA's James Webb Space Telescope looks like a spring flower in full bloom. Once launched into space, the Webb telescope’s 18-segmented gold mirror is specially designed to capture infrared light from the first galaxies that formed in the early universe. http://www.nasa.gov/sites/default/files/thumbnails/image/otis_to_iis-1.jpg

On Saturday April 22, 2017, Expedition 51 Flight Engineer Thomas Pesquet of the European Space Agency photographed Orbital ATK's Cygnus spacecraft as it approached the International Space Station. Using the station's robotic Canadarm2, Cygnus was successfully captured by Pesquet and Commander Peggy Whitson at 6:05 a.m. EDT Saturday morning. http://www.nasa.gov/sites/default/files/thumbnails/image/34040534672_39212f3d5a_o.jpg