Asteroid Tanning in the Solar Wind Salon

Asteroids tan fast in the solar wind (ESO)

In a study carried out by European Southern Observatory (ESO) scientists, it was found that asteroids are susceptible to sunburn. By comparing the material found inside meteorites here on the ground with the colour of asteroids floating in space, there is a huge difference; the asteroids in space are redder.

So far, this might not be too surprising, after all, the surface of Mars is red with ferrous oxides (rust), why shouldn’t asteroids be red too? Actually, asteroids aren’t necessarily made of the same stuff as Mars, and they aren’t getting tanned due to the Sun’s ultraviolet rays; asteroids are bathed in ionizing solar wind particles, causing the asteroid’s surfaces to redden over a period of time. And that period is short when compared with Solar System time scales. It only takes a million years for the surface of young asteroids (born from energetic asteroid collisions) to weather under the constant barrage of particles from the solar wind.

This has some interesting implications for asteroid studies. Possibly the most striking factor this study uncovers is the nature of near-Earth asteroids that have been observed exhibiting comparatively “young” surfaces, apparently free from solar wind reddening. Previously, astronomers have agreed that these young surfaces were down to recent asteroid collisions. However, the period of the solar wind tanning effect is much shorter than asteroid collision frequency. So even if two asteroids collided, in all likelihood, if we observed one of these asteroids, the solar wind would have weathered the surface back to its reddened state.

It turns out that some near-Earth asteroids have “young” surfaces due to gravitational interactions with planets as they pass. When this happens, the red dust is “shaken off”, revealing the untouched rock beneath.

For more, check out my article Young Asteroids Age Fast with a Solar Wind Tan on the Universe Today.

Space Experts to Discuss Threat of Asteroid Impact

Artist impression of a gravitational tractor deflecting the path of an NEO (Dan Durda/B612 Foundation)

Imagine you’re an astronomer who discovered an asteroid. Happy days, you might be able to name it after yourself (99942 O’Neill has a certain ring to it, don’t you think?). At first you feel little concern, after all, we are getting better at spotting near-Earth objects. But when you get news from another observatory that they had been tracking the same object weeks earlier, your interest is piqued. On the one hand, you didn’t technically discover it, but you did confirm its existence. Unfortunately this is probably the one observation you really didn’t want to make. It turns out that this chunk of rock is heading in our direction. And unlike the Earth-grazers that have come before, this asteroid isn’t going to drift past our planet, it isn’t even going to skip off our atmosphere, it’s going to hit us.

Now imagine you are the president of a nation determined to stop the asteroid from hitting Earth. What do you do? Naturally you’d call your team of oil drillers scientific advisors to present your options. One space scientist suggests sending a rocket to the asteroid, strapping it on in the hope it might be nudged out of harms way. The astronomer who made the discovery of the killer asteroid is having a nervous break down in the corner of the room. Your military advisor is urging you to attach a nuclear warhead to your most powerful rocket, in an attempt to obliterate the target. The Secretary of State is calling for restraint; we need to collaborate with other nations, blasting nuclear missiles in to space would violate all kinds of international treaties, wars have been started for less, perhaps someone else has a better idea…?

Although I doubt we’ll ever be fully prepared to act swiftly and decisively in the event of discovering a civilization-ending asteroid, we can at least try. Defending the planet against the ever-present threat of impact is one of the most critical abilities we must develop as a race, ensuring the long-term future of our species. Fortunately, a team of scientists, engineers, policy makers and lawyers (lawyers?) are teaming up to confront this problem…
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