Curious about asteroids? Tune in to tonight’s live stream by expert Lance Benner

Nine radar images of near-Earth asteroid 2007 PA8 were obtained between Oct. 31 and Nov. 13, 2012, by NASA’s 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, Calif. Credit: NASA/JPL-Caltech

Ever wonder how scientists get such detailed radar images of asteroids that only look like points of light in optical telescopes? Tune in tonight or tomorrow night to a talk by Dr. Lance Benner, research scientist at the Jet Propulsion Lab, to find out. Benner will speak on Radar Imaging of Near Earth Asteroids at Pasadena City College; you can watch the real-time webcast and even join the audience for questions after the talk. Both lectures start at 9 p.m. Central (7 p.m. Pacific) time May 9 and 10.

Dr. Lance Benner. NASA photo

Only two radio telescopes on the planet are used for radar imaging of asteroids: the giant 1,000-foot (305 m) Arecibo Observatory in Arecibo, Puerto Rico and the 230-foot (70 m) Goldstone dish in JPL’s Deep Space Network in California’s Mojave Desert. By pinging nearby asteroids with radio waves and studying the reflected radio echoes, these telescopes can resolve details as small as 10 feet (3 m) across.

Radar images can also nail down an asteroid’s rotation rate, measure its position with great precision (allowing for a more precise orbit to be calculated) and “see” features like craters and boulders.

In a related story, Detlef Koschny, Head of Near-Earth Object activities in the European Space Agency’s Space Situational Awareness Programe Office, hopes to improve efforts to find and track near-Earth objects (NEOs) using telescopes operated by European Union members to scan the sky nightly for new Earth-approaching asteroids. The agency is also considering ways of deflecting smaller but still potentially dangerous asteroids should they be found on a collision course with Earth.

“It’s important that we become aware of the current and future position of NEOs, develop estimates on the likelihood of impacts and assess the possible consequences,” says Koschny.

Artist’s view of Earth-approaching asteroids. Many asteroids in this class were originally located a safe distance away in the asteroid belt between Mars and Jupiter, but collisions between them created fragments that were later perturbed by the planet Jupiter into Earth-crossing orbits. Credit: ESA / P. Carril

Of the more than 600,000 known asteroids in the solar system, nearly 10,000 are classified as Near Earth Asteroids because they pass relatively close to our planet. “Near” is defined as any object approaching within 28 million miles of Earth’s orbit.

This week in a meeting in Spain, Deimos Space, an industrial partner working for ESA, invited top researchers from universities, research institutes, national space agencies and industry in Europe and the USA to discuss the state of the art in NEO impact effects and threat mitigation.

There are a variety of methods being considered for changing a potentially hazardous asteroid’s course, and they all critically depend on finding the object well in advance of a collision.

You can hit it with a massive object the way we smacked Comet Tempel 1 with an 815-lb hunk of copper during NASA’s Deep Impact Mission in 2005. If the asteroid’s small enough and impactor massive enough, you could nudge the object off its hazardous course.

Artist view of a spacecraft acting as a gravity tractor nudging an asteroid off-course through mutual gravitational interaction. Earth and moon are off to the right. Credit: Dan Durda/FIAAA/B612 Foundation

Or you could vaporize part of the asteroid with a nuclear weapon, altering its orbit while hopefully not creating additional fragments that could imperil the planet. For obvious reasons, this method would work best with asteroid made of solid rock, not those made of loose “rubble piles”.

Then there’s the gravitational tug method. Here you orbit a large, heavy spacecraft near the asteroid. The mutual gravitational attraction between the two over several years time would change the space rock’s trajectory. A variation on this approach is to fire the spacecraft’s thrusters at the object or even to anchor a rocket engine directly to the asteroid’s surface and blast away, giving it a slow, steady push in the right direction.

Other methods proposed include playing “asteroid paintball” by dusting an NEA with black soot or white powder or even wrapping it in shiny aluminized plastic. Think of how hot you’d feel wearing a black shirt on a sunny day compared to a white one. Absorption or reflection of sunlight can change an asteroid’s rotation rate and nudge it into a slightly different orbit over time.

Expand your knowledge on the topic of asteroids by listening in tonight or tomorrow night to Dr. Benner’s talk. There are actually two ways to connect – the live stream and also via Flash Player with open captioning.

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