The Moon by LRO

Video credit: NASA/GSFC/Arizona State University

Note: For more information, see A Unique View of the Moon.

Bright Explosion on the Moon

For the past 8 years, NASA astronomers have been monitoring the Moon for signs of explosions caused by meteoroids hitting the lunar surface. "Lunar meteor showers" have turned out to be more common than anyone expected, with hundreds of detectable impacts occurring every year.

They've just seen the biggest explosion in the history of the program.

"On March 17, 2013, an object about the size of a small boulder hit the lunar surface in Mare Imbrium," says Bill Cooke of NASA's Meteoroid Environment Office. "It exploded in a flash nearly 10 times as bright as anything we've ever seen before."

Anyone looking at the Moon at the moment of impact could have seen the explosion--no telescope required. For about one second, the impact site was glowing like a 4th magnitude star.

Ron Suggs, an analyst at the Marshall Space Flight Center, was the first to notice the impact in a digital video recorded by one of the monitoring program's 14-inch telescopes. "It jumped right out at me, it was so bright," he recalls.

The 40 kg meteoroid measuring 0.3 to 0.4 meters wide hit the Moon traveling 56,000 mph. The resulting explosion1 packed as much punch as 5 tons of TNT.

Cooke believes the lunar impact might have been part of a much larger event.

"On the night of March 17, NASA and University of Western Ontario all-sky cameras picked up an unusual number of deep-penetrating meteors right here on Earth," he says. "These fireballs were traveling along nearly identical orbits between Earth and the asteroid belt."

This means Earth and the Moon were pelted by meteoroids at about the same time.

“My working hypothesis is that the two events are related, and that this constitutes a short duration cluster of material encountered by the Earth-Moon system," says Cooke.

One of the goals of the lunar monitoring program is to identify new streams of space debris that pose a potential threat to the Earth-Moon system. The March 17th event seems to be a good candidate.

Controllers of NASA's Lunar Reconnaissance Orbiter have been notified of the strike. The crater could be as wide as 20 meters, which would make it an easy target for LRO the next time the spacecraft passes over the impact site. Comparing the size of the crater to the brightness of the flash would give researchers a valuable "ground truth" measurement to validate lunar impact models.

Unlike Earth, which has an atmosphere to protect it, the Moon is airless and exposed. "Lunar meteors" crash into the ground with fair frequency. Since the monitoring program began in 2005, NASA’s lunar impact team has detected more than 300 strikes, most orders of magnitude fainter than the March 17th event. Statistically speaking, more than half of all lunar meteors come from known meteoroid streams such as the Perseids and Leonids. The rest are sporadic meteors--random bits of comet and asteroid debris of unknown parentage.

U.S. Space Exploration Policy eventually calls for extended astronaut stays on the lunar surface. Identifying the sources of lunar meteors and measuring their impact rates gives future lunar explorers an idea of what to expect. Is it safe to go on a moonwalk, or not? The middle of March might be a good time to stay inside.

"We'll be keeping an eye out for signs of a repeat performance next year when the Earth-Moon system passes through the same region of space," says Cooke. “Meanwhile, our analysis of the March 17th event continues.”

Footnote: (1) The Moon has no oxygen atmosphere, so how can something explode? Lunar meteors don't require oxygen or combustion to make themselves visible. They hit the ground with so much kinetic energy that even a pebble can make a crater several feet wide. The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site.

Video credit: NASA

Impact Craters Made by Grail A and B

Lunar Reconnaissance Orbiter Camera image shows the impact site of GRAIL A (Ebb spacecraft) before and after the spacecraft's descent to the lunar surface.

Lunar Reconnaissance Orbiter Camera image shows the impact site of the GRAIL B (Flow spacecraft) impact site before and after the spacecraft's descent to the lunar surface.

Image credit: Top: NASA/GSFC/Arizona State University; Bottom: NASA/GSFC/Arizona State University

Note: For more information, see Lunar Reconnaissance Orbiter Sees GRAIL's Explosive Farewell.

North Polar Gravitational Map of the Moon

This is a polar stereographic map of gravity of the north polar region of the moon from the Gravity Recovery and Interior Laboratory (GRAIL) mission. The map displays the region from latitude 60 north to the pole. The data was collected during GRAIL's extended mission which took place from August 30 to December 17, 2012. In the image, red corresponds to mass excesses and blue and purple to mass deficiencies.

Map credit: NASA/MIT/JPL/GSFC/GRAIL

Note: For more information, see NASA's GRAIL Mission Solves Mystery of Moon's Surface Gravity.

New Image Base for 1:1 Million-Scale Lunar Maps

From the USGS Astrogeology Science Center:

The 1:1 million-scale maps of the Moon in the Gazetteer of Planetary Nomenclature now show the Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) global morphologic map as the base. Previous versions of the maps used the USGS shaded relief and color-coded topography and the USGS Lunar Orbiter mosaics as the base. The previous versions are no longer supported; URLs that linked to these versions have been redirected to the current maps with the LROC WAC image base. For more information, see the page that describes these maps in the Gazetteer of Planetary Nomenclature.

Lunar Gravity Map by Grail

This image shows the variations in the lunar gravity field as measured by NASA's Gravity Recovery and Interior Laboratory (GRAIL) during the primary mapping mission from March to May 2012. Very precise microwave measurements between two spacecraft, named Ebb and Flow, were used to map gravity with high precision and high spatial resolution. The field shown resolves blocks on the surface of about 12 miles (20 kilometers) and measurements are three to five orders of magnitude improved over previous data. Red corresponds to mass excesses and blue corresponds to mass deficiencies. The map shows more small-scale detail on the far side of the moon compared to the nearside because the far side has many more small craters. › See video

Image credit: NASA/JPL-Caltech/MIT/GSFC

Apollo 16 Lunar Rover Grand Prix

Apollo 16 astronauts John Young and Charlie Duke take the lunar rover for a spin on the surface of the moon in this film footage of what became known as the "lunar rover Grand Prix". This footage was shot on 16mm film and is silent.

Video credit: NASA

NASA's GRAIL Spacecraft in Science Collection Phase

An artist's depiction of the twin spacecraft that comprise NASA's Gravity Recovery And Interior Laboratory (GRAIL) mission. During the GRAIL mission's science phase, spacecraft (Ebb and Flow) transmit radio signals precisely defining the distance between them as they orbit the Moon in formation. As the two fly over areas of greater and lesser gravity caused by both visible features, such as mountains and craters, and masses hidden beneath the lunar surface, the distance between the two spacecraft will change slightly. Mission scientists use this information to create a high-resolution map of the Moon's gravitational field. The data will allow scientists to understand what goes on below the lunar surface. This information will increase knowledge of how Earth and its rocky neighbors in the inner solar system developed into the diverse worlds we see today.

Illustration credit: NASA/JPL-Caltech/MIT

Note: See also PIA13965: GRAIL Spacecraft Over the Moon.

Poinsot Crater

This image of the lunar surface was taken by NASA's MoonKAM system onboard the Ebb spacecraft on March 15, 2012. The 42.3-mile-wide (68-kilometer-wide) crater in the middle of the image (with the smaller crater inside) is Poinsot. Crater Poinsot, named for the French mathematician Louis Poinsot, is located on the northern part of the moon's far side.

MoonKAM (Moon Knowledge Acquired by Middle school students), is led by Sally Ride, America's first woman in space, and her team at Sally Ride Science, in collaboration with undergraduate students at the University of California in San Diego. Over 2,700 schools in 52 countries have signed up to participate in MoonKAM.

Photo credit: NASA/Caltech-JPL/MIT/SRS

Note: For more information, see NASA GRAIL Returns First Student-Selected Moon Images.

The Earth from the Moon

This image of the far side of the lunar surface, with Earth in the background, was taken by NASA's MoonKAM system onboard the Ebb spacecraft as part of the first image set taken from lunar orbit from March 15-18, 2012. A little more than half-way up and on the left side of the image is the crater De Forest. Due to its proximity to the southern pole, De Forest receives sunlight at an oblique angle when it is on the illuminated half of the Moon.

MoonKAM (Moon Knowledge Acquired by Middle school students), is led by Sally Ride, America's first woman in space, and her team at Sally Ride Science, in collaboration with undergraduate students at the University of California in San Diego. Over 2,700 schools in 52 countries have signed up to participate in MoonKAM.

Photo credit: NASA/Caltech-JPL/MIT/SRS

Note: For more information, see NASA GRAIL Returns First Student-Selected Moon Images.

Copernicus Crater in Ultraviolet Light

LROC Wide Angle Camera (WAC) visible to ultraviolet portrait of Copernicus Crater, image 458 kilometers (284 miles) wide.

Understanding how scientists determine the relative age of geologic units on the Moon is straightforward, most of the time. One simply follows the law of superposition; what is on top is younger, what is below is older. In some cases, superposition relations are not clear, so scientists then compare crater densities. That is the number of impact craters on a common size of ground. Since impacts occur randomly both in time and on the Moon's surface, any piece of ground has an equal chance of being hit. Over time, the number craters in a given area increases. Simply stated, the older an area the more craters you will find.

Photo credit: NASA/GSFC/Arizona State University

Note: For more information, see Absolute Time.

Tour of the Moon

"Tour of the Moon" takes viewers to several interesting locations on the moon. Tour stops included in this breathtaking journey across the moon's surface are: Orientale Basin, Shackleton crater, South Pole-Aitken Basin, Tycho crater, Aristarchus Plateau, Mare Serenitatis, Compton-Belkovich volcano, Jackson crater and Tsiolkovsky crater.

Video credit: NASA; text credit: NASA.

Evolution of the Moon

"Evolution of the Moon" explains why the moon did not always look like it does now. The moon likely started as a giant ball of magma formed from the remains of a collision by a Mars-sized object with the Earth about four and a half billion years ago. After the magma cooled, the moon's crust formed. Then between 4.5 and 4.3 billion years ago, a giant object hit near the moon's South Pole, forming the South Pole-Aitken Basin, one of the two largest proven impact basins in the solar system. This marked the beginning of collisions that would cause large scale changes to the moon's surface, such as the formation of large basins.

Because the moon had not entirely cooled on the inside, magma began to seep through cracks caused by impacts. Around one billion years ago, it's thought that volcanic activity ended on the near side of the moon as the last of the large impacts made their mark on the surface. The moon continued to be battered by smaller impacts. Some of the best-known impacts from this period include the Tycho, Copernicus, and Aristarchus craters. So, while the moon today may seem to be an unchanging world, its appearance is the result of billions of years of violent activity.

Video credit: NASA

Lunar Mineralogical Map

This image of the Moon is from NASA's Moon Mineralogy Mapper on the Indian Space Research Organization's Chandrayaan-1 mission. It is a three-color composite of reflected near-infrared radiation from the Sun, and illustrates the extent to which different materials are mapped across the side of the Moon that faces Earth.

Small amounts of water and hydroxyl (blue) were detected on the surface of the Moon at various locations. This image illustrates their distribution at high latitudes toward the poles.

Blue shows the signature of water and hydroxyl molecules as seen by a highly diagnostic absorption of infrared light with a wavelength of three micrometers. Green shows the brightness of the surface as measured by reflected infrared radiation from the Sun with a wavelength of 2.4 micrometers, and red shows an iron-bearing mineral called pyroxene, detected by absorption of 2.0-micrometer infrared light.

Photo credit: ISRO/NASA/JPL-Caltech/Brown University/USGS

Update: For more information, see NASA-Funded Scientists Detect Water on Moon's Surface that Hints at Water Below.

A New Map of the Moon

NASA’s Lunar Reconnaissance Orbiter science team released the highest resolution near-global topographic map of the moon ever created. This new topographic map shows the surface shape and features over nearly the entire moon with a pixel scale close to 328 feet.

Although the moon is Earth's closest neighbor, knowledge of its morphology is still limited. Due to the limitations of previous missions, a global map of the moon’s topography at high resolution has not existed until now. With LRO's Wide Angle Camera and the Lunar Orbiter Laser Altimeter instrument, scientists can now accurately portray the shape of the entire moon at high resolution.

For more information on the new lunar map, visit the LRO site.

Image credit: NASA/Goddard Space Flight Center/DLR/ASU

Slumping Rim of the Moon's Darwin C Crater

High incidence angle (83°) accentuates the slumping rim of Darwin C. The parallel fractures along the crater rim are slump blocks pulling away from the rim toward the interior of the crater, which is in shadow (lower right). LROC NAC M148624404R, image is 720 meters across.

Darwin C (20.5°S, 288.9°E) is one of several satellite craters associated with the crater Darwin. Compared to its sister satellite craters, this one is less degraded. However, the rim of Darwin C provides an excellent example of post-impact modification of a crater rim.

Photo credit: NASA/GSFC/Arizona State University

Note: For more information, see Slumping Rim of Darwin C.

Secrets of Schröteri

Vallis Schröteri is a magnificent sinuous rille and of particular interest is its inner rille, which diverges from the primary rille near the arrow. This nested form indicates that multiple eruptive events occurred or there was a large change in the volume of a single eruption over time. LROC WAC mosaic, 100 m/pixel.

LROC NAC close-up of a bend in the inner rille of Vallis Schröteri; the rille walls are visible in the upper left and lower right corners of this image. The arrow in the LROC WAC mosaic above denotes the location of this image; image width is 600 m.

Photo credit: NASA/GSFC/Arizona State University

Note: The large crater in the top image is Herodotus Crater.

Impact Melt Features on Tycho Crater's Floor

Depressions and positive relief features in Tycho crater were caused by a complex mixture of granular material and impact melt settling to the floor. Image width is 370 m, LROC NAC M119923147L.

LROC WAC mosaic with arrow noting the location of the melt features within Tycho crater seen in the NAC image above. Image width is 150 km.

Impact melt creates a wide variety of features on the Moon. These include melt ponds, draped ejecta, viscous flows, linear and nonlinear depressions, and positive relief features. As impact melts mix with loose rock during crater formation, solid pieces of rock stick above the surface of the ponding melt to form little peaks (positive relief features). The depressions are possibly cooling fractures in the melt that result as the melt slowly solidifies and contracts (the opposite of how water behaves when it freezes), however they could also be part of an impact melt drainage network. We don't know for certain know the origin of all of these features, the best way to find out is to have astronauts traverse this terrain while exploring the Moon.

Photo credit: NASA/GSFC/Arizona State University

Block of Ejecta in Tycho Crater

320 meter (1,050 feet) block of ejecta in Tycho crater covered by a veneer of impact melt. Image width is 370 meters (1214 feet), LROC NAC 142334392RE.

LROC WAC context mosaic of Tycho, arrow points to the ejecta block within Tycho. Image width is 150 km.

Tycho crater is a Copernican age crater (85 kilometers, or 53 miles, diameter) located at 43.3° South, 11.2° West. It is named for the 16th century Danish astronomer Tycho Brahe and is one of the most visible features on the near side of the Moon. Its ray system is so obvious and widespread that Apollo 17 astronauts sampled its ejecta, over 2,000 kilometers (1,243 miles) away from the crater. Scientists dated the Tycho samples at about 110 Ma. We also have surface views of Tycho's ejecta blanket taken by the Surveyor 7 soft lander.

Notice the smooth areas on the top of the ejecta block in this NAC frame. Most likely the smooth area is a thin sheet of impact melt. The large block was probably flung up during the impact event, fell back down into the crater, and subsequently covered by impact melt. This series of events must have occurred quickly after the impact, as the melt would solidify soon after forming.

Photo credit: NASA/GSFC/Arizona State University

Rilles As Far As The Eye Can See

LROC WAC mosaic of the rille-rich Prinz crater region. Bench-like features are visible in the Prinz B depression and two flows originating in Prinz B converge just west of the arrow.

The bouldery, higher-reflectance mound in the central portion of this image is an island near the source region, Prinz B, for a short sinuous rille. The two rilles join at the triangular tip of this kipuka-like structure and flow northwestward for ~10 km. Image width is 500 m.

Photo credit: NASA/GSFC/Arizona State University