bookmark_borderHuman Asteroid Initiative

NASA’s FY2014 budget proposal includes a plan to robotically capture a small near-Earth asteroid and redirect it safely to a stable orbit in the Earth-moon system where astronauts can visit and explore it.

Performing these elements for the proposed asteroid initiative integrates the best of NASA’s science, technology and human exploration capabilities and draws on the innovation of America’s brightest scientists and engineers. It uses current and developing capabilities to find both large asteroids that pose a hazard to Earth and small asteroids that could be candidates for the initiative, accelerates our technology development activities in high-powered solar electric propulsion and takes advantage of our hard work on the Space Launch System rocket and Orion spacecraft, helping to keep NASA on target to reach the President’s goal of sending humans to Mars in the 2030s.

When astronauts don their spacesuits and venture out for a spacewalk on the surface of an asteroid, how they move and take samples of it will be based on years of knowledge built by NASA scientists and engineers who have assembled and operated the International Space Station, evaluated exploration mission concepts, sent scientific spacecraft to characterize near-Earth objects and performed ground-based analog missions.

As early as the 1970s, NASA examined potential ways to use existing hardware to visit an asteroid to understand better its characteristics. On the International Space Station, scientific investigations and technology demonstrations are improving knowledge of how humans can live and work in space. The agency also has examined many possible mission concepts to help define what capabilities are needed to push the boundaries of space exploration.

During the early space shuttle flights and through assembly of the space station, NASA has relied on testing both in space and on Earth to try out ideas through a host of analog missions, or field tests, that simulate the complexity of endeavors in space.

Through 16 missions in the National Oceanic and Atmospheric Administration’s underwater Aquarius Reef Base off the coast of Key Largo, Fla., aquanauts have tested techniques for human space exploration. These underwater tests have been built upon the experience gained by training astronauts in the Neutral Buoyancy Laboratory at NASA’s Johnson Space Center in Houston to assemble and maintain the space station. The NASA Extreme Environment Mission Operations (NEEMO) 15 and 16 missions in 2011 and 2012, respectively, simulated several challenges explorers will face when visiting an asteroid, including how to anchor to and move around the surface of a near-Earth object and how to collect samples of it.

NASA also has simulated an asteroid mission as part of its 2012 Research and Technology Studies ground test at Johnson. During the simulation, a team evaluated how astronauts might do a spacewalk on an asteroid and accomplish other goals. While performing a spacewalk on a captured asteroid will involve different techniques than the activities performed during recent analog exercises, decisions made about ways to best sample an asteroid will be informed by the agency’s on-going concept development and past work.

Scientific missions also have investigated the nature of asteroids to provide a glimpse of the origins of the solar system. From the Pioneer 10 spacecraft, which in 1972 was the first to venture into the Main Asteroid Belt, to the Dawn mission, which recently concluded its investigations of asteroid Vesta and is on its way to the dwarf planet Ceres, NASA’s forays help us understand the origins of the solar system and inform decisions about how to conduct missions to distant planetary bodies. Scientists both at NASA and across the world also continue to study asteroids to shed light on their unique characteristics.

As NASA ventures farther into the solar system, the agency continues to simulate and evaluate operations and technical concepts for visiting an asteroid.

bookmark_borderAsteroids Impact On Earth

WASHINGTON — Research by NASA and international scientists concludes giant asteroids, similar or larger than the one believed to have killed the dinosaurs, hit Earth billions of years ago with more frequency than previously thought.

To cause the dinosaur extinction, the killer asteroid that impacted Earth 65 million years ago would have been almost 6 miles (10 kilometers) in diameter. By studying ancient rocks in Australia and using computer models, researchers estimate that approximately 70 asteroids the same size or larger impacted Earth 1.8 to 3.8 billion years ago. During the same period, approximately four similarly-sized objects hit the moon.

“This work demonstrates the power of combining sophisticated computer models with physical evidence from the past, further opening an important window to Earth’s history,” said Yvonne Pendleton, director of NASA’s Lunar Science Institute (NLSI) at NASA’s Ames Research Center at Moffett Field, Calif.

Evidence for these impacts on Earth comes from thin rock layers that contain debris of nearly spherical, sand-sized droplets called spherules. These millimeter-scale clues were formerly molten droplets ejected into space within the huge plumes created by mega-impacts on Earth. The hardened droplets then fell back to Earth, creating thin but widespread sedimentary layers known as spherule beds.
The new findings are published today in the journal Nature.

“The beds speak to an intense period of bombardment of Earth,” said William Bottke principal investigator of the impact study team at the Southwest Research Institute (SwRI) in Boulder, Colo. “Their source long has been a mystery.”

The team’s findings support the theory Jupiter, Saturn, Uranus and Neptune formed in different orbits nearly 4.5 billion years ago, migrating to their current orbits about 4 billion years ago from the interplay of gravitational forces in the young solar system. This event triggered a solar system-wide bombardment of comets and asteroids called the “Late Heavy Bombardment.” In the paper, the team created a model of the ancient main asteroid belt and tracked what would have happened when the orbits of the giant planets changed. They discovered the innermost portion of the belt became destabilized and could have delivered numerous big impacts to Earth and the moon over long time periods.

At least 12 mega-impacts produced spherule beds during the so-called Archean period 2.5 to 3.7 billion years ago, a formative time for life on Earth. Ancient spherule beds are rare finds, rarer than rocks of any other age. Most of the beds have been preserved amid mud deposited on the sea floor below the reach of waves.

The impact believed to have killed the dinosaurs was the only known collision over the past half-billion years that made a spherule layer as deep as those of the Archean period. The relative abundance of the beds supports the hypothesis for many giant asteroid impacts during Earth’s early history.

The frequency of the impacts indicated in the computer models matches the number of spherule beds found in terrains with ages that are well understood. The data also hint at the possibility that the last impacts of the Late Heavy Bombardment on Earth made South Africa’s Vredefort crater and Canada’s Sudbury crater, both of which formed about 2 billion years ago.

“The Archean beds contain enough extraterrestrial material to rule out alternative sources for the spherules, such as volcanoes,” said Bruce Simonson, a geologist from Oberlin College in Oberlin, Ohio.

The research was funded by NLSI and conducted by members or associates of NLSI’s Center of Lunar Origin and Evolution, based at SwRI.

The impact study team also includes scientists from Purdue University in West Lafayette, Ind.; Charles University in Prague, Czech Republic; Observatorie de la Cote d’Azur in Nice, France; and Academia Sinica in Taipei, Taiwan.

To learn about the NLSI, visit:

http://lunarscience.arc.nasa.gov