Another moon for Earth


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Astronomers have discovered an asteroid whose solar orbit is almost identical to Earth’s, and has it hovering so near the Earth that it is almost another moon.

Based on orbital data the scientists estimate that the asteroid, between 300 to 1000 feet in diameter, has been hovering near Earth for the past 775 years, and it will only drift away in about 165 years from now.

Correction: Engineer and regular reader James Fincannon emailed me to note that this asteroid really doesn’t have an orbit “almost identical to the Earth.” As he wrote, “Seems to go between Venus and Mercury and then all the way out to Mars! It seems to pass by Earth occasionally.” Thus, this recent period of closeness is only a temporary one.

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7 comments

  • wodun

    Good candidate for a visit?

  • Pzatchok

    Good candidate for a test move.

    Can we move it into a better permanent lunar or Earth orbit?

  • James Fincannon

    Not a good candidate for a test move since it is so big. The Asteroid Redirect Mission has a goal of no more than 10 m diameter. This one is >10 times that!

    Also, the orbit (from <Venus to ~Mars) is so vastly different from Earth's that the energy involved in changing the orbit would be prohibitive.

    In the old days, mass drivers were suggested to spit off material of the asteroid , aimed in the right direction, to move them around. We are a little far from that today.

    However, I have wondered if there was a way to hitch a ride on these objects. You could obviously use impactors, but usually they have limited capability. Landing nicely on one would take too much energy though.

  • Pzatchok

    Nothing is too big.

    We just have to scale up our engine and fuel.
    And possibly change our plan on the speed of the move. Even if it takes a few years to move it into final position whats the loss?

  • James Fincannon

    Too much fuel, too many launch vehicles. A 9 m diameter asteroid would weigh 1,300,000kg believe it or not (upper limit =3.5 g/cm^3). It would take about ~9000 kg of Xenon fuel for a “reasonable orbit” asteroid (it only goes from 1-1.17AU from the Sun, fairly close to Earth’s orbit) and 8 years trip time. A 100 m diameter asteroid would weigh ~1.8 billion kg. That’s 12 million kg of Xenon by simple scaling. And this is what is needed for a “reasonable orbit” asteroid at that size (effectively 1400 ARMs). But the “quasi Moon” goes from .55AU to 1.45AU from the Sun, plus a sizable inclination difference which uses alot more energy to move towards that of Earth’s. That is way beyond simple scaling. Sure you can take longer, but then your components start to wear out, especially the power and propulsion system.

  • Pzatchok

    So the harvesting of asteroids is impossible and should just be forgotten about?

    And I believe Xenon is only used because it offers the smallest package in fuels size.

    And if this small asteroid can never be moved then deflecting one from hitting the Earth most be just as much of a waste of time?
    Unless we use a nuclear bomb right?

    And who said it had to be just one engine and fuel package at one time?
    This might take more than one lifetime to make its final move into orbit.

  • James Fincannon

    Mining asteroids and returning the materials that were mined is within reason. Moving a massive asteroid from an orbit radically different from Earth to an orbit close to Earth’s is not within reason at this time. However, if the asteroid is within certain size limits and orbit limits, it can be moved with current technology.

    Regarding Xenon’s use, most experience is with it. Iodine, Bismuth and Zinc (and even Magnesium) seem to be even better if deposition issues and thruster life issues can be addressed. (High Density Hall Thruster Propellant Investigations, James Szabo, et al. ,48th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 30 July – 01 August 2012, Atlanta, Georgia).

    The trick to deflecting an asteroid seems to be identifying one that may impact Earth and doing this many years prior to the possible impact date and then pushing slightly on it to get it to miss. This does not mean a massive orbit change. This is a slight nudge done over years. This is reasonable as long as we know for sure which direction to nudge it!

    I have heard that nuclear bombs are not the best approach. although I never quite saw why. It seems like if you break up the object into small enough objects to burn up in the atmosphere, then that would work. But what I have read suggested we would just end up with a radioactive massive object hitting us.

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