This area will cover relevant news of the threat to the planet from Near Earth Objects (NEOs) including concepts and designs for mitigation. All opinions are those of the author.

11 March 2008

Article on Earth's Fate in the Future Solar System (and How to Use an Asteroid/Comet to Change this Fate)

This is a very interesting article on the calculated fate of the Earth as the Sun changes over the next few billion years. Please read the entire article. Near the end there is mention of an interesting thought experiment of how the Earth could avoid getting swallowed by the expanding Sun using the orbits or asteroids/comets (late on another author had the idea to use solar radiation pressure from a sail, both abstracts are below). Here is that excerpt from the end of the article along with more information on the concept...

- Selections from NYTimes Article...

Is there any way out of this fiery end for the robots or cockroaches or whoever will be running the Earth in a billion years?

One option is to leave for another planet or another star system.

Another option, Dr. Smith [Robert Connon Smith of the University of Sussex in England] said, is to engage in some large-scale high-stakes engineering.

In the same way that space probes can get a trajectory boost by playing gravitational billiards with Venus or Jupiter to gain speed and get farther out in space, so the Earth could engineer regular encounters with a comet or asteroid, thus raising its orbit and getting farther from the Sun, according to a paper in 2001 by Don Korycansky and Gregory Laughlin of the University of California, Santa Cruz, and Fred Adams of the University of Michigan.

Dr. Laughlin said that when their paper first came out, they were praised by the radio host Rush Limbaugh and other conservatives for forward thinking.

But Dr. Laughlin said they were actually not advocating the orbit-shifting project, noting that a miscalculation could lead to the comet’s hitting the Earth.

“There are profound ethical issues involved,” he wrote in an e-mail message, “and the cost of failure (an Earth-sterilizing impact) is unacceptably high.”

Anyway, such a maneuver would prolong the viability of the Earth for only a few billion years. After that, the planet would be stranded in the cold and dim

Article: Kissing the Earth Goodbye in About 7.59 Billion Years
Dennis Overbye
New York Times
11 March 2008

Link: NYTimes Article: Kissing the Earth Goodbye in About 7.59 Billion Years

Article: "Recipe for Saving Earth: Move It"
Robert Roy Britt
07 February 2001

Link: Article: "Recipe for Saving Earth: Move It"

- Abstract (using asteroids/comets to move the Earth)

Astronomical Engineering: A Strategy For Modifying Planetary Orbits
Journal: Astrophysics and Space Science
Issue: Volume 275, Number 4 / March, 2001
Authors: D.G. Korycansky, Gregory Laughlin and Fred C. Adams

D.G. Korycansky, CODEP Dept Earth Sciences, University of California, Santa Cruz, CA 95064, USA

Gregory Laughlin, NASA Ames Research Center, 245-3 Moffett Field, CA 94035, USA

Fred C. Adams, Physics Department, University of Michigan, Ann Arbor, MI 48109, USA

Abstract: The Sun's gradual brightening will seriously compromise the Earth's biosphere within sim 109 years. If Earth's orbit migrates outward,however, the biosphere could remain intact over the entir emain-sequence lifetime of the Sun. In this paper, we explore the feasibility of engineering such a migration over a long time period. The basic mechanism uses gravitational assists to (in effect)transfer orbital energy from Jupiter to the Earth, and thereby enlarges the orbital radius of Earth. This transfer is accomplished by a suitable intermediate body, either a Kuiper Belt object or a mainbelt asteroid. The object first encounters Earth during an inward pass on its initial highly elliptical orbit of large (sim 300 AU) semimajor axis. The encounter transfers energy from the object to the Earth in standard gravity-assist fashion by passing close to the leading limb of the planet. The resulting outbound trajectory of the object must cross the orbit of Jupiter; with proper timing, the outbound object encounters Jupiter and picks up the energy it lost to arth. With small corrections to the trajectory, or additional planetary encounters (e.g., with Saturn), the object can repeat this process over many encounters. To maintain its present flux of solar energy, the Earth must experience roughly one encounter every 6000years (for an object mass of 1022 g). We develop the details of this scheme and discuss its ramifications.

Link: Springer Journal Article Link

- Abstract (using solar radiation pressure to move the Earth)

Astronomical Engineering Revisited: Planetary Orbit Modification Using Solar Radiation Pressure

Journal: Astrophysics and Space Science
Issue: Volume 282, Number 4 / December, 2002
Author Colin R. McInnes

Colin R. McInnes, Department of Aerospace Engineering, University of Glasgow, Glasgow, G12 8QQ, Scotland, U.K.

Abstract: As the Sun evolves along the main sequence its luminosity will grow, leading to a steadily increasing solar flux at the Earth with corresponding catastrophic consequences for the biosphere. A novel means of avoiding this terminal route to human evolution has recently been proposed by Korycansky et al. which utilises a series of grazing fly-pasts of the Earth with a small solar system body to increase the orbit radius of the Earth over a timescale of order 109 years. This short paper will propose an alternative strategy which utilises a large reflective sail to generate a propulsive thrust due to solar radiation pressure. It will be shown that if the sail is configured to be in static equilibrium relative to the Earth, the centre-of-mass of the Earth-sail system slowly accelerates. This scheme offers some advantages in that the mass of the sail is four orders of magnitude less than the mass to be processed in the scheme of Korycanskyet al. for trajectory correction manoeuvres alone. In addition, the severe hazard posed by multiple grazing fly-pasts of the Earth by a small solar system body is avoided. Although offering significant advantages, any thoughts of engineering on an astronomical scale clearly requires a leap of the imagination and a ready use of liberal assumptions.

Link: Springer Journal Article Link

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