How to defend the earth from the asteroids.



How to defend the earth from the asteroids.

A collection of images from the WISE spacecraft of the 2305 King asteroid, which bears the name of Martin Luther King Jr. The asteroid appears as a series of orange dots because it is a set of exhibitions that have been added to show its movement through the sky. These infrared images have been color coded so that we can perceive them with the human eye: 3.4 microns are represented in blue; 4.6 microns is green, 12 microns is yellow and 22 microns are shown in red. From the WISE data, we can calculate that the asteroid is approximately 12.7 kilometers in diameter, with a reflectivity of 22%, which indicates a possible stony composition. Credit: NASA

In only 17-20 meters in diameter, the Chelyabinsk meteorite caused extensive damage to the ground and numerous injuries when it exploded on impact with Earth's atmosphere in February 2013.

To avoid another similar impact, Amy Mainzer and her colleagues use a simple but ingenious way to detect these small near-Earth objects (NEO) as they move toward the planet. She is the principal investigator of NASA's asteroid-hunting mission at the Jet Propulsion Laboratory in Pasadena, California, and will describe the work of the NASA Planetary Defense Coordination Office this week at the April Meeting of the NASA American Physical Society in Denver, including your team's NEO recognition method and how it will help efforts to prevent future impacts on Earth.

"If we find an object just a few days after the impact, it greatly limits our options, so in our search efforts we have focused on finding NEO when they are farthest away from Earth, providing the maximum amount of time and opening a space more wide range of mitigation possibilities, "said Mainzer.

But it's a difficult task, like detecting a piece of coal in the night sky, Mainzer explained. "NEOs are intrinsically weak because they are mostly very small and far away from us in space," he said. "Add to this the fact that some of them are as dark as the printer's toner, and trying to detect them against the black of space is very difficult."

How to defend the earth from the asteroids.

An image of the proposed mission of the Near Earth Object Camera (NEOCam), which is designed to find, track and characterize asteroids and comets that approach Earth. Using a thermal infrared camera, the mission would measure the heat signatures of NEOs regardless of whether they are light or dark in color. The telescope's housing is painted black to efficiently radiate its own heat into space, and its sunscreen allows you to observe close to the Sun, where the NEOs in the most Earth-like orbits spend much of their time. In the background there is a set of images of the main belt asteroids collected by the NEOWISE mission prototype; The asteroids appear as red dots on the stars and background galaxies. Credit: NASA

Instead of using visible light to detect incoming objects, the Mainzer team at JPL / Caltech has taken advantage of a characteristic feature of the NEO: its heat. Asteroids and comets are heated by the sun and, therefore, glow intensively at thermal (infrared) wavelengths, which makes them easier to detect with the wide-field infrared scanner's telescope. objects close to Earth (NEOWISE).

"With the NEOWISE mission we can detect objects regardless of the color of their surface and use them to measure their sizes and other surface properties," said Mainzer.

The discovery of the surface properties of NEO provides Mainzer and his colleagues with an idea of ​​how large the objects are and what they are made of, both critical details in mounting a defensive strategy against a NEO that threatens the Earth.

For example, a defensive strategy is to physically "push" a NEO away from an impact path on Earth. But to calculate the energy required for that push, the details of the NEO mbad, and therefore the size and composition, are necessary.

How to defend the earth from the asteroids.

On August 28, 2015, the NEOWISE space telescope spotted the comet C / 2013 US10 accelerating on Earth. This comet entered from the Oort cloud, the shell of cold, frozen material that surrounds the Sun in the most distant part of the solar system. beyond the orbit of Neptune. NEOWISE captured the comet when it was full of activity caused by the heat of the sun. On November 15, 2015, the comet made its closest approach to the Sun, submerging itself within the orbit of the Earth; this may be the first time this ancient comet has been so close to the Sun. NEOWISE observed the comet at two heat-sensitive infrared wavelengths, 3.4 and 4.6 microns, which are color-coded as cyan and red in this image . NEOWISE detected this comet several times in 2014 and 2015; Five of the exhibits are shown here in a combined image representing the movement of the comet across the sky. The copious amounts of gas and dust thrown by the comet appear red in this image because they are very cold, much colder than the background stars. Credit: NASA

Astronomers also think that examining the composition of asteroids will help understand how the solar system was formed.

"These objects are intrinsically interesting because some are believed to be as old as the original material that made up the solar system," Mainzer said. "One of the things we have found is that NEOs are very diverse in composition."

Mainzer is now ready to take advantage of advances in camera technology to help in the search for NEO. "We are proposing to NASA a new telescope, the Near Earth Object Camera (NEOCam), to do a much more complete job of mapping the locations of the asteroids and measuring their sizes," Mainzer said.

NASA is not the only space agency that tries to understand NEOs. For example, the Hayabusa 2 mission of the Japan Aerospace Exploration Agency (JAXA) Hayabusa 2 plans to collect samples from an asteroid. And in his presentation, Mainzer will explain how NASA works with the global space community in an international effort to defend the planet from the impact of NEO.


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More information:
The presentation, "NASA's Planetary Defense Coordination Office at NASA headquarters," will take place on Tuesday, April 16, in the Governor's Square 14 room at the Sheraton Denver Downtown Hotel. Summary: meetings.aps.org/Meeting/APR19/Session/X05.1

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American Physical Society


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