Together with irregular galaxies, spiral galaxies make up approximately 60 percent of the galaxies in the local universe. However, despite their prevalence, each spiral galaxy is unique — like snowflakes, no two are alike. This is demonstrated by the striking face-on spiral galaxy NGC 6814. http://www.nasa.gov/sites/default/files/thumbnails/image/hubble_friday_05132016.jpg

This photograph shows NASA’s newest Deep Space Network antenna, Deep Space Station 35 (DSS-35) in Canberra, Australia. The Deep Space Network is managed by the Space Communications and Navigation (SCaN) program office, created on May 16, 2006. http://www.nasa.gov/sites/default/files/thumbnails/image/dss35c.jpg

Astronauts aboard the International Space Station (ISS) see the world at night on every orbit — that’s 16 times each crew day. An astronaut took this broad, short-lens photograph of Earth’s night lights while looking out over the remote reaches of the central equatorial Pacific Ocean. http://www.nasa.gov/sites/default/files/thumbnails/image/iss044e045215_lrg.jpg

Expedition 47 Flight Engineer Tim Kopra of NASA posted this May 15, 2016 photograph to social media, writing, "Water etchings in western @Mexico sands. @Space_Station #Explore" https://www.nasa.gov/sites/default/files/styles/full_width_feature/public/thumbnails/image/iss047e122077a.jpg

Flames from the solid rocket boosters lit up the clouds of smoke and steam trailing behind shuttle Atlantis on May 19, 2000, as it lifted off on mission STS-101. It was the shuttle program's third space station assembly flight, and first space flight for astronaut Jeff Williams, currently aboard the station as a member of the Expedition 47 crew. http://www.nasa.gov/sites/default/files/thumbnails/image/sts101-s-007.jpg

CubeSats fly free after leaving the NanoRacks CubeSat Deployer on the International Space Station on May 17, 2016. Seen here are two Dove satellites. The satellites are part of a constellation designed, built and operated by Planet Labs Inc. to take images of Earth from space. http://www.nasa.gov/sites/default/files/thumbnails/image/26512620163_904c1a34f8_o.jpg

Cassini orbited in Saturn's ring plane -- around the planet's equator -- for most of 2015. http://www.nasa.gov/sites/default/files/thumbnails/image/pia20481-1041.jpg

On May 19, 2016, NASA's IceBridge, an airborne survey of polar ice, crossed Greenland to fly central glacier flowlines in the east-central region of the country. This photo captures the fjord of Violin Glacier, with Nord Glacier at the upper left corner. This is IceBridge's eighth spring campaign of science flights over Arctic sea and land. http://www.nasa.gov/sites/default/files/thumbnails/image/violinglacier.jpg

NASA's OSIRIS-REx spacecraft is revealed after its protective cover is removed inside the Payload Hazardous Servicing Facility at Kennedy Space Center, on May 21, 2016. OSIRIS-REx, targeted for a Sept. 8 launch, will be the first U.S. mission to sample an asteroid, retrieve at least two ounces of surface material and return it to Earth for study. http://www.nasa.gov/sites/default/files/thumbnails/image/ksc-20160521-ph_dng0001_0066.jpg

Mars has bright polar caps of ice that are easily visible from telescopes on Earth. A seasonal cover of carbon-dioxide ice and snow is observed to advance and retreat over the poles during the Martian year. Scientists using radar data have found a record of the most recent Martian ice age recorded in the north polar ice cap. http://www.nasa.gov/sites/default/files/thumbnails/image/mars_polar_deposits_main.jpg

Former NASA astronaut Scott Kelly speaks about his historic mission aboard the International Space Station during an event at the United States Capitol Visitor Center, Wednesday, May 25, 2016, in Washington. http://www.nasa.gov/sites/default/files/thumbnails/image/27197314521_68a25511c9_o.jpg

An astronaut aboard the International Space Station used a powerful lens to photograph these three reefs in Australia’s Great Barrier Reef on Oct. 12, 2015. Reefs are easy to spot from space because the iridescent blues of shallow lagoons contrast sharply with the dark blues of deep water. http://www.nasa.gov/sites/default/files/thumbnails/image/iss045e056257_lrg.jpg

New stars are the lifeblood of our galaxy, and there is enough material revealed by this Herschel infrared image to build stars for millions of years to come. http://www.nasa.gov/sites/default/files/thumbnails/image/pia13500.jpg

NASA’s New Horizons spacecraft took this stunning image of Pluto only a few minutes after closest approach on July 14, 2015. The image was obtained at a high phase angle –that is, with the sun on the other side of Pluto, as viewed by New Horizons. Seen here, sunlight filters through and illuminates Pluto’s complex atmospheric haze layers. http://www.nasa.gov/sites/default/files/thumbnails/image/darksideimage_unann.png

This 10.5-billion-year-old globular cluster, NGC 6496, is home to heavy-metal stars of a celestial kind! The stars comprising this spectacular spherical cluster are enriched with much higher proportions of metals — elements heavier than hydrogen and helium are curiously known as metals in astronomy — than stars found in similar clusters. http://www.nasa.gov/sites/default/files/thumbnails/image/hubble_friday_06032016.jpg

Expedition 47 Flight Engineer Tim Peake of the European Space Agency photographed rare, high-altitude noctilucent or "night shining" clouds from the International Space Station on May 29, 2016. Noctilucent clouds form between 76 to 85 kilometers (47 to 53 miles) above the Earth’s surface, near the boundary of the mesosphere and thermosphere. https://www.nasa.gov/sites/default/files/styles/full_width_feature/public/thumbnails/image/27420333805_6fd1876a46_o.jpg

Sand dunes cover much of this terrain, which has large boulders lying on flat areas between the dunes. It is late winter in the southern hemisphere of Mars, and these dunes are just getting enough sunlight to start defrosting their seasonal cover of carbon dioxide. Spots form where pressurized carbon dioxide gas escapes to the surface. http://www.nasa.gov/sites/default/files/thumbnails/image/27002215442_179da57f4b_o.jpg

A view of the Neutron star Interior Composition Explorer (NICER) X-ray Timing Instrument without its protective blanketing shows a collection of 56 close-packed sunshades. NICER, an upcoming NASA astrophysics mission, will uncover the physics governing the ultra-dense interiors of neutron stars. http://www.nasa.gov/sites/default/files/thumbnails/image/image_2_nicer.jpg

This stunning Earth image taken by the Expedition 47 crew on May 31, 2016, from the International Space Station looks from northwestern China on the bottom into eastern Kazakhstan. The large lake in Kazakhstan with golden sun glint is the crescent-shaped Lake Balkhash, the second largest lake in Central Asia. http://www.nasa.gov/sites/default/files/thumbnails/image/27250243350_5563fbc72b_o.jpg

The drizzle of stars scattered across this image forms a galaxy known as UGC 4879. UGC 4879 is an irregular dwarf galaxy — as the name suggests, galaxies of this type are a little smaller and messier than their cosmic cousins, lacking the majestic swirl of a spiral or the coherence of an elliptical. http://www.nasa.gov/sites/default/files/thumbnails/image/hubble_friday_06102016.jpg