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Long-Ago Giant Impact May Have Created Moon's Mysterious Grooves — **Grooves and gashes associated with the Imbrium Basin on the moon have long been puzzling. New research suggests some of these features were formed after a protoplanet slammed into the moon long ago.**
**Credit: NASA/Northeast Planetary Data Center/Brown University**

A baby planet at least as large as New Jersey that smashed into the moon billions of years ago might have created the mysterious grooves that score the lunar surface, a new study suggests.

This finding could shed light on a violent era of impacts that once bombarded Earth and the rest of the inner solar system, researchers said.

Scientists investigated the area surrounding Mare Imbrium — Latin for "The Sea of Showers." This dark patch on the northwest quadrant on the near side of moon, the side that faces Earth, makes up the right eye of the "Man in the Moon." [The Moon: 10 Surprising Lunar Facts]

Mare Imbrium lies within the Imbrium Basin, the largest basin on the near side of moon. Previous research suggested that the 720-mile-wide (1,160 kilometers) basin was created by a giant ancient cosmic impact, and was later filled with vast lakes of lava that cooled to become dark rock.

Mare Imbrium is surrounded by grooves and gashes large enough to be seen from Earth even with small telescopes. These features, together known as the Imbrium Sculpture, are concentrated on Imbrium Basin's southeast side.

Many elements of the Imbrium Sculpture radiate from the center of Imbrium Basin like spokes on a wheel. Previous research had suggested that the Imbrium Basin and Imbrium Sculpture were created by a giant asteroid impact about 3.8 billion years ago. This asteroid was apparently traveling from the northwest to the southeast and collided with the moon at an oblique angle rather than straight on, with debris spraying southeast along this trajectory.

However, in addition to features radiating from Imbrium Basin's center, prior work discovered another set of grooves in the Imbrium Sculpture that did not spread out from the heart of the basin. Instead, they apparently came from a region northwest of the basin's center.

Trajectories of debris ejected from the Imbrium impact basin on the moon determined by the orientations of grooves and elongate secondary craters (along with locations of the Apollo landing sites). One set does not converge; rather, it forms parallel trends that correspond to the fragments originating from different portions of the Imbrium asteroid, rather than ejecta from the moon.
**Credit: Peter Schultz**

"This second set of grooves was a real mystery," study lead author Peter Schultz, an impact specialist at Brown University in Providence, Rhode Island,said in a statement. "No one was quite sure where they came from."

But Schultz and co-author David Crawford, of Sandia National Laboratories in Albuquerque, New Mexico, may have solved the mystery. Their results suggest that the Imbrium Basin and Imbrium Sculpture were likely formed by a giant asteroid large enough to be classified as a protoplanet, or baby planet.

To learn more about the impact that might have created the Imbrium, Schultz and Crawford performed hypervelocity-impact experiments using the Vertical Gun Range at NASA's Ames Research Center in Mountain View, California. These experiments involved a 14-foot (4.25 meters) cannon that fired small bullets at up to about 11,200 mph (18,000 km/h), while high-speed cameras and impact plates recorded details about the collisions.

The scientists found that, during a low-angle impact, a high-speed projectile often started breaking up after making contact with a surface. The bottom of the projectile would create a crater, while the sides and top of the projectile would shear off and continue traveling at high speeds along the projectile's original trajectory to scour the surface. The grooves from these chunks would appear to originate from a point slightly offset from the crater generated by the bulk of the projectile — a gap about equal to the distance between the bottom of the projectile and its top and sides. [Asteroid Basics: A Space Rock Quiz]

The researchers suggest that the mystery grooves of the Imbrium Sculpture were etched by chunks that sheared off the sides and top of the impacting asteroid when it hit the moon.

"For Imbrium, as much as 25 percent of the asteroid may have detached from the actual collision," Schultz told Space.com. "Some of the fragments actually escaped the moon entirely."

Computer models analyzing these grooves helped the scientists estimate the size of this "Imbrium Asteroid." Previous estimates suggested that the Imbrium Asteroid was only about 50 miles (80 km) wide. But these new findings suggest that the impactor was actually about 150 miles (250 km) across, or about the length of New Jersey.

Comparison of scours produced by the impactor in experiments (above) and those produced in a computational model of a 100-kilometer-diameter asteroid (red pattern, below). Physical processes affecting the fate of the projectile observed in the lab experiments at high speeds also apply at much larger scale.
**Credit: Peter Schultz**

"That's actually a low-end estimate," Schultz said in a statement. "It's possible that it could have been as large as 300 kilometers [185 miles]."

The scientists also found that several other basins on the moon may have been created by oblique impacts from protoplanets. For instance, they estimated that the Moscoviense and Orientale basins on the moon's far side may have been created by asteroids about 62 and 68 miles (100 and 110 km) across, respectively — larger than previous estimates.

All in all, the researchers suggest that protoplanets may have once been common in the asteroid belt. "The large basins we see on the moon and elsewhere are the record of lost giants," Schultz said in a statement.

Material from protoplanets smashing into thhttp://www.space.com/e moon could help explain why lunar samples that NASA's Apollo missions brought back to Earth had high levels of meteoritic rock. This was especially true of the Apollo 16 mission, which landed downrange from the Imbrium impact.

The scientists added that collisions with these protoplanets might explain many of the impacts that battered the moon and the rest of the inner solar system during a violent era known as the Late Heavy Bombardment between 4.1 billion and 3.7 billion years ago. Thousands of chunks that sheared off the Imbrium Asteroid and other protoplanets would have kept going after impact, flying off into space to continue striking other bodies.

"These chips off the old blocks could have contributed significantly to the impact record we see on the moon and other terrestrial planets," Schultz said in a statement.

Schultz and Crawford detailed their findings online today (July 20) in thejournal Nature.

Follow Charles Q. Choi on Twitter @cqchoi. Follow us @Spacedotcom,Facebookand Google+. Original article on Space.com.

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**The Perseid meteor shower.**
**Credit: SKY2015 | Shutterstock.com**

Someday, stargazers may see pink, green and violet shooting stars streak across the night sky, thanks to a startup company that wants to launch tiny, human-made meteors, according to news sources.

The Japanese company ALE plans to create and release artificial meteors into space that emit colorful trails when they burn up in Earth's atmosphere. For instance, a meteor made of copper would burn green; a barium one would burn blue; and potassium, rubidium and cesium meteors would burn various shades of purple.

"As one learns in high school science classes, when a substance burns, the flame emits a specific color; this is called the flame reaction," ALE said on its website. "By loading our satellite with various materials, we are able to turn our shooting stars into any color." [Space-y Tales: The 5 Strangest Meteorites]

Normally, shooting stars form when particles in space — usually much smaller than an inch (just a few millimeters long) enter the atmosphere and burn brightly, in a process known as plasma emission. ALE researchers want to recreate that process, but with human-made particles, they said.

The company plans to launch a satellite carrying about 500 to 1,000 "source particles," which will become the artificial meteors. Once the satellite stabilizes in orbit, operators on the ground can command it to discharge the particles to create the colorful shooting stars.

"The particles will travel about one-third of the way around the Earth and enter the atmosphere," ALE researchers said. "[They] will then begin plasma emission and become shooting star[s]" at an altitude of about 37 miles to 50 miles [60 to 80 kilometers] aboveground.

The mission, dubbed "Sky Canvas Project," will emit dozens, if not hundreds, of particles, showering Earth with rainbow-colored meteor showers, the company said.

Though small, the particles will burn brightly, according to ALE scientists. Sirius, the brightest star in the night sky, has an apparent magnitude of minus 1.5. (The lower the apparent magnitude, the brighter the glow.) The artificial shooting stars have an apparent magnitude of about minus 1, at least in a laboratory setting, the researchers said. This means they'll bevisible down on Earth, even in a city, where lights often drown out celestial objects, ALE said. [Fallen Stars: A Gallery of Famous Meteorites]

Space junk

If launched, ALE's satellite would join countless other spacecraft orbiting Earth. However, the company says it will follow international regulations and ensure that its satellite doesn't stay aloft and become space junk, by purposefully crashing it into the atmosphere within 25 years.

"In this case, the used satellite itself will become a very large shooting star," ALE said.

Moreover, the company is taking precautions so that its meteor-emitting satellite won't crash into other satellites. The team created software based on the United States' Joint Space Operations Center (JSpOC), which tracks satellites and debris in space. ALE will calculate where other objects are located in space, and prevent the ALE satellite from colliding with them, the company said.

But Moriba Jah, a space-junk expert and the director of the University of Arizona's Space Object Behavioral Sciences program, isn't sure that method will work.

JSpOC's site, space-track.org, largely tracks objects' general movements, but not their precise locations, which makes him "a bit uncomfortable" and unsure if ALE's satellite can effectively stay out of trouble, Jah told National Geographic.

Still, ALE plans to launch its first satellite in the second half of 2017 and service it in 2018, the researchers said. The company plans to launch a new satellite every year after that, and it hopes the project will reveal more about the science of meteors. [Photos: New Kind of Meteorite Found in Sweden]

But it won't be cheap. Each particle is slated to cost about 1 million yen (about $9,620) to produce, and that doesn't include the costs for the satellite or the launch, National Geographic reported.

What's more, ALE dispelled rumors last week that it might stage an artificial meteor shower for the 2020 Olympic Games in Tokyo.

"While we do intend on providing our shooting stars, once complete, to large-scale events — and we also have mentioned the Olympic Games as an event that we would love to work with (*hint*) in interviews — we have not made an official proposal to the Tokyo Organising Committee of the Olympic and Paralympic Games and hence do not have any facts or developments to disclose at the moment," the company said in a statement.

Original article on Live Science.