In Mars' Wirtz Crater, these dunes are likely active. http://www.nasa.gov/sites/default/files/thumbnails/image/pia22869.jpg

This Hubble Space Telescope mosaic is of a portion of the immense Coma cluster of over 1,000 galaxies, located 300 million light-years from Earth. http://www.nasa.gov/sites/default/files/thumbnails/image/stsci-h-p1844b-q-4571x2571.png

Soyuz MS-11 spacecraft launched from the Baikonur Cosmodrome in Kazakhstan to bring a new crew to begin their six and a half month mission on the International Space Station. http://www.nasa.gov/sites/default/files/thumbnails/image/45248114015_bf5ebaf3e9_k.jpg

This image of the horizon is as it was seen from the cockpit of NASA Armstrong Flight Research Center’s F/A-18 research aircraft. http://www.nasa.gov/sites/default/files/thumbnails/image/afrc2018-0287-193small.jpg

Experiments in forest observation, protein crystal growth and in-space fuel transfer demonstration are heading to the International Space Station following the launch Wednesday of SpaceX’s 16th mission. http://www.nasa.gov/sites/default/files/thumbnails/image/45473446114_7d5e5d6fe2_o.jpg

International Space Station Commander Alexander Gerst viewed SpaceX’s Dragon cargo craft chasing the orbital laboratory on Dec. 8, 2018 and took a series of photos. http://www.nasa.gov/sites/default/files/thumbnails/image/45532312914_2634bd334e_k.jpg

Less than three months into its mission, NASA’s Ice, Cloud and land Elevation Satellite-2, or ICESat-2, is already exceeding scientists’ expectations. http://www.nasa.gov/sites/default/files/thumbnails/image/seaice11.jpg

The Washington National Cathedral is seen lit up with space imagery prior to the Smithsonian National Air and Space Museum's Spirit of Apollo event commemorating the 50th anniversary of Apollo 8, Tuesday, Dec. 11, 2018 in Washington, DC. http://www.nasa.gov/sites/default/files/thumbnails/image/spirit_of_apollo_washington_national_cathedral_for_50th_anniversary_of_apollo_8_0.jpg

NASA astronauts Anne McClain (background) and Serena Auñón-Chancellor are pictured inside the U.S. Destiny laboratory module aboard the International Space Station. http://www.nasa.gov/sites/default/files/thumbnails/image/iss057e114340_0.jpg

Before electricity, water fountains worked by relying on gravity to channel water from a higher elevation to a lower one. In space, awesome gaseous fountains have been discovered in the centers of galaxy clusters. http://www.nasa.gov/sites/default/files/thumbnails/image/a2597_0.jpg

For most of human history, we mortals have dreamed of taking to the skies. Then, 115 years ago on on December 17, 1903, Orville and Wilbur Wright achieved the impossbile. http://www.nasa.gov/sites/default/files/thumbnails/image/wrightflyer.jpg

Engineers built a tank identical to the Space Launch System tank that will be flown on Exploration Mission-1, the first flight of Space Launch System and the Orion spacecraft for testing. http://www.nasa.gov/sites/default/files/thumbnails/image/maf_20181126_p_lh2_lift_onto_aft_sim-42.jpg

SpaceX’s Crew Dragon spacecraft and Falcon 9 rocket are positioned at the company’s hangar at Launch Complex 39A at NASA’s Kennedy Space Center in Florida, ahead of the test targeted for Jan. 17, 2019. http://www.nasa.gov/sites/default/files/thumbnails/image/dm-1-20181218-129a8083-2-apprvd.jpg

Russian Search and Rescue teams arrive at the Soyuz MS-09 spacecraft shortly after it landed with Expedition 57 crew members. http://www.nasa.gov/sites/default/files/thumbnails/image/32518530168_88a2729274_k_1.jpg

Fifty years ago on Dec. 21, 1968, Apollo 8 launched from Pad A, Launch Complex 39, Kennedy Space Center at 7:51 a.m. ES). http://www.nasa.gov/sites/default/files/thumbnails/image/s68-56050.jpg

NASA lost seven of its own on the morning of Jan. 28, 1986, when a booster engine failed, causing the Shuttle Challenger to break apart just 73 seconds after launch. In this photo from Jan. 9, 1986, the Challenger crew takes a break during countdown training at NASA's Kennedy Space Center. http://www.nasa.gov/sites/default/files/images/722342main_challenger_full_full.jpg

Falcon 9, Crew Dragon Roll to Launch Pad http://www.nasa.gov/sites/default/files/thumbnails/image/46907789351_b5d7dddb42_o.jpg

Portions of Cuba, the Bahamas and the Turks and Caicos Islands are viewed from the International Space Station. http://www.nasa.gov/sites/default/files/thumbnails/image/31988314307_fdfcdbd0b0_k.jpg

Despite the vastness of space, objects tend to get in front of each other. http://www.nasa.gov/sites/default/files/thumbnails/image/bedin1.png

On Jan. 22, 2003, the crew of Space Shuttle Columbia captured this sunrise from the crew cabin during Flight Day 7. http://www.nasa.gov/sites/default/files/thumbnails/image/s107e05485.jpg