NASA Administrator Charles Bolden, left, and NASA Deputy Administrator Dava Newman take part in a "Day of Remembrance" ceremony to pay tribute to the crews of Apollo 1 and Space Shuttles Challenger and Columbia at Arlington National Cemetery on Jan. 28.
Millions watched in horror as the shuttle carrying high school teacher Christa McAuliffe exploded shortly after takeoff on Jan. 28, 1986.
Gallery: 30 Years Since the Challenger Disaster
Win McNamee / Getty Images
Comet 67P/Churyumov-Gerasimenko's small lobe and its distinctive Hatmehit depression face directly towards the Rosetta spacecraft in this view from Jan. 21. The spacecraft was 49 miles from the nucleus of the comet.
Rosetta was launched in 2004. In August 2014, it made headlines by deploying the Philae lander to the comet's surface, 317 million miles from Earth.
JM GUILLON / AFP - Getty Images
An Ariane 5 rocket launches late on Jan. 27 from Kourou, French Guiana, carrying the first communications satellite of the new generation Intelsat Epic NG.
Astronaut Scott Kelly tweeted this view of the the spectacular colors of the Bahamas seen from the International Space Station with the comment, "Watercolors!" Kelly has been tweeting dazzling views of the Earth's surface with the hastag #EarthArt.
Photos: Astronaut Tweets Startling Views of Australia
BORIS HORVAT / AFP - Getty Images
Arnaud Prost, an engineer at France's Compagnie Maritime d'Expertises, or Comex, greets a jogger as he tests the "Gandolfi 2" underwater training suit for on Jan. 20 in Marseille, France.
The suit, developed with the European Space Agency (ESA), is designed to help astronaut's prepare for spacewalks.
A massive snowstorm churns over the East Coast of the United States on Jan. 23 as seen from the International Space Station.
LEONHARD FOEGER / Reuters
The moon rises above the trees near the Streif alpine ski course in Kitzbuehel, Austria,on Jan. 22.
NASA/ESA via AFP - Getty Images
The star cluster Trumpler 14 is featured in this image captured by the Hubble Space Telescope and released on Jan. 21. One of the largest gatherings of hot, massive and bright stars in the Milky Way, this cluster houses some of the most luminous stars in our entire galaxy.
Scott Kelly / NASA
An aurora glows over Canada in this view from the International Space Station on Jan. 20.
The neon green comes from the interaction between electrically charged particles from the sun and atoms high up in Earth's atmosphere.
An artist's rendering released Jan. 20 shows "Planet Nine," the name Caltech researchers have given to a new planet possibly lurking in the outer reaches of our solar system. The planet, if it exists, has a mass 10 times that of Earth and takes between 10,000 and 20,000 years to orbit the sun.
R. Hurt / Artist's Rendering: Caltech via Reuters
A Zinnia plant pillow floats through the U.S. Destiny Laboratory aboard the International Space Station on Jan. 22. The zinnias are part of the flowering crop experiment that began last year on Nov. 16 when NASA astronaut Kjell Lindgren activated the Veggie system and its rooting "pillows" containing zinnia seeds. The challenging process of growing the zinnias provided an exceptional opportunity for scientists back on Earth to better understand how plants grow in microgravity and for astronauts to practice doing what they'll be tasked with on a deep space mission: autonomous gardening.
ESO via AFP - Getty Images
A European Southern Observatory telescope in Chile captured this image released on Jan. 25 of galaxy IC 1613. Unusually clean and small, it
contains very little cosmic dust, allowing astronomers to explore its contents with great clarity.
PETER KOMKA / EPA
A halo glows around the moon above Salgotarjan, Hungary, on Jan. 17. The halo phenomenon is produced by light interacting with ice crystals suspended in the atmosphere, resulting in a wide variety of colored or white rings, arcs and spots in the sky.
NASA / Reuters
British astronaut Tim Peake performs his first spacewalk at the International Space Station on Jan. 15. Peake became the first British astronaut to walk in space when he left the station to fix a power station problem.
The spiral galaxy NGC 4845, located over 65 million light-years away in the constellation of Virgo appears in this NASA/ESA Hubble Space Telescope image released on Jan. 8. The galaxy's orientation clearly reveals the galaxy's striking spiral structure: a flat and dust-mottled disc surrounding a bright galactic bulge. NGC 4845's glowing center hosts a gigantic version of a black hole, known as a supermassive black hole.
The Year in Space Pictures: 2015
NASA via Reuters