NASA Articles


NASA’s NEOWISE mission has recently discovered some celestial objects traveling through our neighborhood, including one on the blurry line between asteroid and comet. Another–definitely a comet–might be seen with binoculars through next week.

An object called 2016 WF9 was detected by the NEOWISE project on Nov. 27, 2016. It’s in an orbit that takes it on a scenic tour of our solar system. At its farthest distance from the sun, it approaches Jupiter’s orbit. Over the course of 4.9 Earth-years, it travels inward, passing under the main asteroid belt and the orbit of Mars until it swings just inside Earth’s own orbit. After that, it heads back toward the outer solar system. Objects in these types of orbits have multiple possible origins; it might once have been a comet, or it could have strayed from a population of dark objects in the main asteroid belt.

2016 WF9 will approach Earth’s orbit on Feb. 25, 2017. At a distance of nearly 32 million miles (51 million kilometers) from Earth, this pass will not bring it particularly close. The trajectory of 2016 WF9 is well understood, and the object is not a threat to Earth for the foreseeable future.

A different object, discovered by NEOWISE a month earlier, is more clearly a comet, releasing dust as it nears the sun. This comet, C/2016 U1 NEOWISE, “has a good chance of becoming visible through a good pair of binoculars, although we can’t be sure because a comet’s brightness is notoriously unpredictable,” said Paul Chodas, manager of NASA’s Center for Near-Earth Object (NEO) Studies at the Jet Propulsion Laboratory in Pasadena, California.

As seen from the northern hemisphere during the first week of 2017, comet C/2016 U1 NEOWISE will be in the southeastern sky shortly before dawn. It is moving farther south each day and it will reach its closest point to the sun, inside the orbit of Mercury, on Jan. 14, before heading back out to the outer reaches of the solar system for an orbit lasting thousands of years. While it will be visible to skywatchers at Earth, it is not considered a threat to our planet either.

NEOWISE is the asteroid-and-comet-hunting portion of the Wide-Field Infrared Survey Explorer (WISE) mission. After discovering more than 34,000 asteroids during its original mission, NEOWISE was brought out of hibernation in December of 2013 to find and learn more about asteroids and comets that could pose an impact hazard to Earth. If 2016 WF9 turns out to be a comet, it would be the 10th discovered since reactivation. If it turns out to be an asteroid, it would be the 100th discovered since reactivation.

What NEOWISE scientists do know is that 2016 WF9 is relatively large: roughly 0.3 to 0.6 mile (0.5 to 1 kilometer) across.

It is also rather dark, reflecting only a few percent of the light that falls on its surface. This body resembles a comet in its reflectivity and orbit, but appears to lack the characteristic dust and gas cloud that defines a comet.

“2016 WF9 could have cometary origins,” said Deputy Principal Investigator James “Gerbs” Bauer at JPL. “This object illustrates that the boundary between asteroids and comets is a blurry one; perhaps over time this object has lost the majority of the volatiles that linger on or just under its surface.”

Near-Earth objects (NEOs) absorb most of the light that falls on them and re-emit that energy at infrared wavelengths. This enables NEOWISE’s infrared detectors to study both dark and light-colored NEOs with nearly equal clarity and sensitivity.

“These are quite dark objects,” said NEOWISE team member Joseph Masiero, “Think of new asphalt on streets; these objects would look like charcoal, or in some cases are even darker than that.”

NEOWISE data have been used to measure the size of each near-Earth object it observes. Thirty-one asteroids that NEOWISE has discovered pass within about 20 lunar distances from Earth’s orbit, and 19 are more than 460 feet (140 meters) in size but reflect less than 10 percent of the sunlight that falls on them.

The Wide-field Infrared Survey Explorer (WISE) has completed its seventh year in space after being launched on Dec. 14, 2009.

Data from the NEOWISE mission are available on a website for the public and scientific community to use. A guide to the NEOWISE data release, data access instructions and supporting documentation are available at:

Access to the NEOWISE data products is available via the on-line and API services of the NASA/IPAC Infrared Science Archive.

A list of peer-reviewed papers using the NEOWISE data is available at:


In the “Star Wars” universe, ice, ocean and desert planets burst from the darkness as your ship drops out of light speed. But these worlds might be more than just science fiction.

Some of the planets discovered around stars in our own galaxy could be very similar to arid Tatooine, watery Scarif and even frozen Hoth, according to NASA scientists.

Sifting through data on the more than 3,400 confirmed alien worlds, scientists apply sophisticated computer modeling techniques to tease out the colors, light, sunrise and sunsets we might encounter if we could pay them a visit.

Some of these distant worlds are even stranger than those that populate the latest “Star Wars” film, “Rogue One.” And others are eerily like the fictional planets from a galaxy far, far away.

Planets with double suns


A real planet in our galaxy reminded scientists so much of Luke Skywalker’s home planet, they named it “Tatooine.” Officially called Kepler-16b, the Saturn-sized planet is about 200 light-years away in the constellation Cygnus. The reality of its two suns was so startling, George Lucas himself agreed to the astronomers’ nickname for the planet.

“This was the first honest-to-goodness real planetary system where you would see the double sunset as two suns,” said Laurance Doyle, an astrophysicist with the Search for Extraterrestrial Intelligence Institute and Director of the Institute for the Metaphysics of Physics, who discovered the planet using NASA’s Kepler space telescope in 2011.

A person on Kepler-16b would have two shadows. In a storm, two rainbows would appear. Each sunset would be unique, because the stars are always changing their configuration. Building a sundial would require calculus.

Astronomers have discovered that about half of the stars in our Milky Way galaxy are pairs, rather than single stars like our sun. So while Kepler-16b aka Tatooine is probably too cold and gaseous to be home to life, or a hopeful desert farm boy, it’s a good bet that there might be a habitable Tatooine “twin” out there somewhere.

Desert worlds

Jakku, Jedha

George Lucas has a fondness for desert planets, and at least one NASA scientist thinks he’s on the right track.

“Desert planets are possible. We have one right here in our solar system in Mars. We think desert planets elsewhere could be even more habitable than Mars is,” said Shawn Domagal-Goldman, an astrobiologist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

He likes Lucas’ proliferation of arid worlds because he believes it might reflect the galaxy we live in.

“The recurring theme of desert worlds in ‘Star Wars’ is really interesting, because there is some research that shows that these would be likely habitable worlds to find,” said Domagal-Goldman, who is, among other things, a climate scientist.

Desert worlds are not only a very real possibility, but they are probably very common, he said. They could be hot, like Tatooine and Jakku, or cold, like Mars and Jedha in “Rogue One.”

“The lack of water on a desert planet might be what makes it more habitable. Water amplifies changes to climates and can cause planets to end up being really hot like Venus, or really cold like Europa,” said Domagal-Goldman.

Ice planets


There is a world named Hoth in our galaxy-an icy super-Earth discovered in 2006. It reminded scientists so much of the frozen Rebel base they unofficially nicknamed it after the planet that appears in “The Empire Strikes Back.” The planet’s scientific designation is OGLE 2005-BLG-390L, after the Optical Gravitational Lensing Experiment (OGLE) that found it.

Our galaxy’s Hoth is too cold to support life as we know it. But life may evolve under the ice of a different world, or a moon in our solar system. On Earth, it’s been found inside volcanoes, deep ocean trenches, even the frozen soil of Antarctica.

NASA is currently designing a Europa mission to look for life under the crust of Jupiter’s icy moon Europa. And Saturn’s moon Enceladus also contains an underground ocean that could harbor alien life.

Ocean worlds

Kamino, Scarif

For the scientists that characterize exoplanets, the most important planet to study is Earth-the only known planet with life. And life on Earth began in the ocean.

“We need Earth climate science to help us understand planetary habitability and the potential diversity of life on exoplanets,” said astrobiologist Nancy Kiang, a research scientist at NASA’s Goddard Institute for Space Studies. As an astrobiologist, her job is to model the kind of plant life that might exist on planets around other stars-also known as exoplanets.

We haven’t confirmed the existence of ocean worlds like the perpetually rainy Kamino in “Attack of the Clones,” or worlds with oceans, like the beachy Scarif from “Rogue One.” But we have found frozen ocean worlds in our solar system, in the moons Europa and Enceladus.

We may even be able to glimpse an ocean on an exoplanet in the not-so-distant future.

“Ocean glint can be detected over large distances,” said Victoria Meadows, a professor at the University of Washington and director of the NASA Astrobiology Institute’s Virtual Planetary Laboratory.

Such a glint was first observed reflecting from the liquid methane seas on Titan, the largest moon of Saturn.

Forest worlds

Endor, Takodana

Both the forest moon of Endor, from “Return of the Jedi,” and Takodana, the home of Han Solo’s favorite cantina in “The Force Awakens,” are green like our home planet. But astrobiologists think that plant life on other worlds could be red, black, or even rainbow-colored.

A few months ago, astronomers from the European Southern Observatory announced the discovery of Proxima Centauri b, a planet only four light-years away from Earth, which orbits a tiny red star.

“The star color would be peachy to the human eye,” Meadows said. “And the planet would appear dark purple to light purple, looking at it from a spacecraft.” From the surface of Proxima b, the sky would appear to be periwinkle.

The light from a red star, also known as an M dwarf, is dim and mostly in the infrared spectrum, as opposed to the visible spectrum we see with our sun. The planet also doesn’t have sunrises or sunsets like Earth: one side always faces its sun.

“If you have photosynthetic organisms, they would always get fixed amounts of light all the time. It would be a permanent sunset around the planet. You would see a gradation of color,” she said.

Just as seaweed changes color from green to dark brown as you dive deeper into the ocean, plants on a red dwarf planet may brilliantly change color from the day side to the night side.

And that could mean rainbow plant life.

Inhabited worlds

Just about any ‘Star Wars’ planet

In the “Star Wars” universe, Lucas and company envision scores of worlds bustling with intelligent beings. In our galaxy, we know of only one such world so far-Earth. But NASA exoplanet scientists think we have a fighting chance of finding life beyond our solar system.

The next few years will see the launch of a new generation of spacecraft to search for planets around other stars. The Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope will attempt to determine what’s in the atmospheres of other planets. Then, in the next decade, the Wide Field Infrared Survey Telescope (WFIRST) will bring us images of exoplanets around sun-like stars.

That’s one step closer to finding life.

“The idea of life on other planets resonates with people on a very personal level,” Doug Hudgins, NASA’s program scientist for exoplanet exploration, said of the “Star Wars” films enduring popularity. “They portray this image of a universe that is teeming with life.”

“We are at our heart explorers,” he said. “We want to know what’s out there. Through the imaginings of George Lucas and Gene Roddenberry, we get to feel for a bit of time like we really can go out and explore the stars.”


Scientists used NASA`s Curiosity Mars rover in recent weeks to examine slabs of rock cross-hatched with shallow ridges that likely originated as cracks in drying mud.

“Mud cracks are the most likely scenario here,” said Curiosity science team member Nathan Stein. He is a graduate student at Caltech in Pasadena, California, who led the investigation of a site called “Old Soaker,” on lower Mount Sharp, Mars.


If this interpretation holds up, these would be the first mud cracks — technically called desiccation cracks — confirmed by the Curiosity mission. They would be evidence that the ancient era when these sediments were deposited included some drying after wetter conditions. Curiosity has found evidence of ancient lakes in older, lower-lying rock layers and also in younger mudstone that is above Old Soaker.

“Even from a distance, we could see a pattern of four- and five-sided polygons that don`t look like fractures we`ve seen previously with Curiosity,” Stein said. “It looks like what you`d see beside the road where muddy ground has dried and cracked.”

The cracked layer formed more than 3 billion years ago and was subsequently buried by other layers of sediment, all becoming stratified rock. Later, wind erosion stripped away the layers above Old Soaker. Material that had filled the cracks resisted erosion better than the mudstone around it, so the pattern from the cracking now appears as raised ridges.

The team used Curiosity to examine the crack-filling material. Cracks that form at the surface, such as in drying mud, generally fill with windblown dust or sand. A different type of cracking with plentiful examples found by Curiosity occurs after sediments have hardened into rock. Pressure from accumulation of overlying sediments can cause underground fractures in the rock. These fractures generally have been filled by minerals delivered by groundwater circulating through the cracks, such as bright veins of calcium sulfate.

Both types of crack-filling material were found at Old Soaker. This may indicate multiple generations of fracturing: mud cracks first, with sediment accumulating in them, then a later episode of underground fracturing and vein forming.

“If these are indeed mud cracks, they fit well with the context of what we`re seeing in the section of Mount Sharp Curiosity has been climbing for many months,” said Curiosity Project Scientist Ashwin Vasavada of NASA`s Jet Propulsion Laboratory in Pasadena. “The ancient lakes varied in depth and extent over time, and sometimes disappeared. We`re seeing more evidence of dry intervals between what had been mostly a record of long-lived lakes.”

Besides the cracks that are likely due to drying, other types of evidence observed in the area include sandstone layers interspersed with the mudstone layers, and the presence of a layering pattern called cross-bedding. This pattern can form where water was flowing more vigorously near the shore of a lake, or from windblown sediment during a dry episode.

Scientists are continuing to analyze data acquired at the possible mud cracks and also watching for similar-looking sites. They want to check for clues not evident at Old Soaker, such as the cross-sectional shape of the cracks.

The rover has departed that site, heading uphill toward a future rock-drilling location. Rover engineers at JPL are determining the best way to resume use of the rover`s drill, which began experiencing intermittent problems last month with the mechanism that moves the drill up and down during drilling.

Curiosity landed near Mount Sharp in 2012. It reached the base of the mountain in 2014 after successfully finding evidence on the surrounding plains that ancient Martian lakes offered conditions that would have been favorable for microbes if Mars has ever hosted life. Rock layers forming the base of Mount Sharp accumulated as sediment within ancient lakes billions of years ago.

On Mount Sharp, Curiosity is investigating how and when the habitable ancient conditions known from the mission`s earlier findings evolved into conditions drier and less favorable for life. For more information about Curiosity, visit:


A new study of the first year of observational data from NASA’s Soil Moisture Active Passive (SMAP) mission is providing significant surprises that will help in modeling Earth’s climate, forecasting our weather and monitoring agricultural crop growth.

The findings are presented in a paper published recently in the journal Nature Geosciences by scientists from the Massachusetts Institute of Technology (MIT), Cambridge; and NASA’s Jet Propulsion Laboratory, Pasadena, California. They used SMAP measurements to estimate soil moisture memory in the top 2 inches (5 centimeters) of Earth’s topsoils. The estimates improve upon earlier ones that were predicted from models or based on sparse data from ground observation stations. Soil moisture memory, which refers to how long it takes for soil moisture from rainfall to dissipate, can influence our weather and climate.

The team found that, on average, about one-seventh of the amount of rain that falls is still present in the topmost layer of soils three days later. This persistence is greatest in Earth’s driest regions.

The top 2 inches of topsoil on Earth’s land masses contains an infinitesimal fraction of our planet’s water — less than one-thousandth of one percent. Yet because of its position at the interface between land and atmosphere, that tiny amount plays a crucial role in everything from agriculture, weather, climate and even the spread of disease. This thin layer is a key part of the global water cycle over the continents and is also a key factor in the global energy and carbon cycles.

The behavior and dynamics of this moisture reservoir have been hard to quantify and analyze, however, because soil moisture measurements have been slow and laborious to make, or too sparse for researchers to make general conclusions. That situation changed in 2015 with the launch of SMAP, designed to provide high-quality, globally comprehensive and frequent measurements of the moisture in that top layer of soil.

“SMAP’s ability to collect soil moisture data samples every two to three days over the globe gives scientists an unprecedented tool for tracking changes in soil moisture over time,” said SMAP Project Scientist Simon Yueh of JPL, a study co-author. “For the first time, we can accurately quantify these rainfall memory effects on soil moisture on a global scale and for various types of land cover.”

Our ocean, containing 97 percent of Earth’s water, plays a major role in storing and releasing heat. Over land, the moisture in the topmost layer of the soil also stores and releases heat, albeit through different mechanisms. That moisture “is a tiny, tiny fraction of the water budget, but it’s sitting at a very critical zone at the surface of the land, and plays a disproportionately critical role in the cycling of water,” says SMAP Science Team Leader and study co-author Dara Entekhabi of MIT.

Among the study’s other findings, the team found that SMAP data identify regions where soil moisture memory has the potential to influence weather and affect and amplify droughts and floods. When moisture evaporates from wet soil, it cools the soil in the process, but when the soil gets too dry, that cooling diminishes. This, in turn, can lead to hotter weather and heat waves that extend and deepen drought conditions. Such effects had been speculated, but hadn’t been directly studied until now.

To read more about the NASA/National Science Foundation-funded study, visit:

SMAP launched Jan. 31, 2015, on a minimum three-year mission to map global soil moisture and detect whether soils are frozen or thawed. The mission is designed to help scientists understand the links between Earth’s water, energy and carbon cycles; reduce uncertainties in Earth system modeling; and enhance our ability to monitor and predict natural hazards like floods and droughts. SMAP data have additional practical applications, including improved weather forecasting and crop yield predictions.

SMAP is managed for NASA’s Science Mission Directorate in Washington by JPL, with instrument hardware and science contributions made by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. To learn more about SMAP, visit:

NASA collects data from space, air, land and sea to increase our understanding of our home planet, improve lives and safeguard our future. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.