Why the Asteroid Threat Should be Taken Seriously by David Eicher (Astronomy Magazine, April 6)


….The press response to the Asteroid Day [http://www.asteroidday.org] announcement was spectacular — I think, fair to say, beyond anyone’s expectations. Although it should be said that whenever Brian May does something, it certainly attracts attention, and the same could also be said of Martin Rees, who is one of the most brilliant people on the planet. The announcement found itself plastered throughout numerous newspapers and online media the world over. The attention was explosive, and certainly was also helped from the inclusion of two ex-astronauts, Ed Lu and Rusty Schweickart, under whose guidance the B612 Foundation has tackled the asteroid threat. This forward-looking organization focuses on the asteroid impact danger and proposes a future Sentinel mission to thwart a potential large space rock with Earth’s name on it. They were also joined by the ubiquitous Bill Nye, president of the Planetary Society, who did an excellent job of explaining the realities of asteroid impact dangers….

The question arises, then: What exactly is our current best knowledge about the real danger of future impacts? To help answer this, I consulted a number of planetary scientists and read voluminous papers from others. Gradually, a clear picture of reality began to crystallize….

Asteroid impact expert Alan Harris, now retired from JPL, estimates that 200 million objects equal to or greater than 6 meters across are in Earth-crossing orbits. Harris, in fact, is the one who has produced population studies, most recently in 2012 and 2014, that have been quoted and used by Chodas and others. According to Harris, objects 6 meters or larger across strike Earth about once every two years. Roughly 10 million Chelyabinsk-sized objects are in Earth-crossing orbits and the impact…

A 1- to 2-kilometer asteroid not only causes local and regional devastation, but it also strikes with such force and delivers so much energy that it casts a large amount of material far up into the atmosphere such that it comes down globally. Modelers of the resulting nuclear winter scenario believe such an impact ignites widespread catastrophic fires and blots out sunlight, permanently altering the planet’s ecosystem. It is this problem that wiped out the dinosaurs, who otherwise by rights should exist still today, and enabled small mammalian survivors to carry on, in need of only modest amounts of food, to evolve 66 million years later into human beings…. The bottom line? A 1- or 2-kilometer asteroid will impact Earth, on average, about once every million years, and could produce a global catastrophe….

Understanding the risks from asteroid impacts on Earth is a pretty young exercise, as is the case with much of astronomy and planetary science. We now know that future dangerous impacts will happen, though they may be many years away. From a planetary scientist’s view, however, it would be grossly negligent to avoid completing as thorough a survey as possible of all the space rocks in Earth-crossing orbits and understanding other small bodies farther out in the solar system that could come our way.

It is an insurance policy for planet Earth. We should not be alarmed as concerned human beings. But we should be determined, informed, and on the clock, keeping track of the solar system and its movements. One day they will interact again in a big way with our planet. Perhaps we will discover incoming asteroids and be able to divert their orbit before disaster strikes. We damn sure will want to be ready when that day comes. Anything less would be a reckless misuse of the knowledge our species has worked so hard to gain.


Further Confusion Over ARM (April 9)

NASAwatch reports that the NASA Advisory Council Wants to Cancel Asteroid Redirect Mission and Send it to Phobos Instead


Two tweets from today’s meeting of the NAC: Steve Squyres: We are looking for a real mission – not just tech development – and as supportive of mission to Mars as possible. Tom Young: This is a kinder, gentler way of terminating ARM. Should take the $1.25 billion and apply it to things to take people to Mars.

Note: NASA, the OMB, and the President’s Office of Science and Technology POloicy still support the ARM B option.

An Opinion column in Spaceflight Insider (April 5) also criticizes ARM: “Asteroid Redirect Mission – Option B as in Boondoggle”



ESA’s Planetary Defense Test Set for 2020. (Astrobiology Magazine, April 2)


This month marked the start of preliminary design work on ESA’s Asteroid Impact Mission, or AIM. Intended to demonstrate technologies for future deep-space missions, AIM will also be the Agency’s very first investigation of planetary defence techniques. Launched in October 2020, AIM will travel to a binary asteroid system – the paired Didymos asteroids, which will come a comparatively close 11 million km to Earth in 2022. The 800 m-diameter main body is orbited by a 170 m moon, informally called ‘Didymoon’. This smaller body is AIM’s focus: the spacecraft will perform high-resolution visual, thermal and radar mapping of the moon to build detailed maps of its surface and interior structure….

AIM is Europe’s contribution to the larger Asteroid Impact & Deflection Assessment mission: AIDA. In late 2022, the NASA-led part of AIDA will arrive: the Double Asteroid Redirection Test, or DART, probe will approach the binary system – then crash straight into the asteroid moon at about 6 km/s. “AIM will be watching closely as DART hits Didymoon,” explains Ian Carnelli, managing the mission for ESA. “In the aftermath, it will perform detailed before-and-after comparisons on the structure of the body itself, as well as its orbit, to characterise DART’s kinetic impact and its consequences….

“The results will allow laboratory impact models to be calibrated on a large-scale basis, to fully understand how an asteroid would react to this kind of energy. This will shed light on the role the ejecta plume will play – a fundamental part in the energy transfer and under scientific debate for over two decades. “In addition, DART’s shifting of Didymoon’s orbit will mark the first time humanity has altered the dynamics of the Solar System in a measurable way.

“It will also give us a baseline for planning any future planetary defence strategies. We will gain insight into the kind of force needed to shift the orbit of any incoming asteroid, and better understand how the technique could be applied if a real threat were to occur.”…


NEO News (now in its twentieth year of distribution) is an informal compilation of news and opinion dealing with Near Earth Objects (NEOs) and their impacts. These opinions are the responsibility of the individual authors and do not represent the positions of NASA, Ames Research Center, the International Astronomical Union, or any other organization. If anyone wishes to copy or redistribute original material from these notes, fully or in part, please include this disclaimer.

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