A giant asteroid named Apophis has a one in 45,000 chance of hitting the Earth in 2036. If it did hit the earth it could destroy a city or a region. A slate of new proposals for addressing the asteroid menace was presented today at a recent meeting of the American Association for the Advancement of Science in San Francisco.
One of the Lifeboat Foundation projects is an Asteroid Shield and the issues and points discussed are in direct alignment with Lifeboat. The specific detection and deflection projects are in the Lifeboat Asteroid Shield project.
Edward Lu of NASA has proposed “gravitational tractor” is a spacecraft—up to 20 tons (18 metric tons)—that it could divert an asteroid’s path just by thrusting its engines in a specific direction while in the asteroid’s vicinity.
Scientists also described two massive new survey-telescope projects to detect would-be killer asteroids.
One, dubbed Pan-STARRS, is slated to begin operation later this year. The project will use an array of four 6-foot-wide (1.8-meter-wide) telescopes in Hawaii to scan the skies.
The other program, the Large Synoptic Survey Telescope in Chile, will use a giant 27.5-foot-wide (8.4-meter-wide) telescope to search for killer asteroids. This telescope is scheduled for completion sometime between 2010 and 2015.
David Morrison, an astronomer at NASA’s Ames Research Center, said that “the rate of discoveries is going to ramp up. We’re going to see discoveries being made at 50 to 100 times the current rate.”
“You can expect asteroids like Apophis [to be found] every month.”
Schweickart, the former astronaut, thinks the United Nations needs to draft a treaty detailing standardized international measures that will be carried out in response to any asteroid threat.
His group, the Association of Space Explorers, has started building a team of scientists, risk specialists, and policymakers to draft such a treaty, which will be submitted to the UN for consideration in 2009.
Civilization killing asteroid is predicted to hit Earth around every 100 million years. It is extremely unlikely that it is going to hit us in the next 50–100 years.. We should monitor asteroids and plan for them but the risk is extremely low.
But we cannot be sure of when the next one will hit without a complete survey. Plus the asteroid dangers are ones that we can very affordably take actions against. Unlike some other risks and dangers which are more costly. Plus there are other scientific and economic advantages in more advanced space capablities.
The risks of smaller asteroids that can destroy regions is about one every 1000 years
http://www.space.com/scienceastronomy/asteroid_risk_021009.html
An improved estimate of the number of nearby asteroids still capable of causing local destruction suggests these pesky rocks are likely to hit Earth about once every 1,000 years (Harris’ estimate is uncertain by a factor of about three.) Astronomers had thought such minor catastrophes occurred about once per century.
The new calculations, from Alan Harris of the Space Science Institute in Boulder, CO, show there are about 500,000 relatively small asteroids that inhabit roughly the same region of space through which Earth orbits. The asteroids are in the 50–75 meter (165−245 foot) size range.
Rocks this size can flatten a forest and would cause tremendous damage and even death if it hit a city.
From page 13 of this pdf
http://www.esa.int/gsp/NEO/doc/NEOMAP_report_June23_wCover.pdf
Table 1.1. The estimated frequency and effects of impactors as a function of size.
Impactor size (m) Mean impact Energy released
interval (yr) (megatons TNT)
30 200 2 — Fireball, shock-wave, minor damage.
50 2500 10 Tunguska explosion or small crater.
100 5000 80 Largest H-bomb detonation.
200 47,000 600 Destruction on national scale.
500 200,000 10,000 Destruction on European scale.
1000 600,000 80,000 Many millions dead, global effects.
5000 20 million 10 million Billions dead, global climate change.
10,000 100 million 80 million Extinction of human civilization.
Note: The energy release estimates assume a density of 3500 kg m-3 (stony body) and an impact velocity of 20 km s-1.
Being able to steer away those 200-500m rocks would be good and definitely the 1000-5000m and 5000m+ rocks.
Plus the intervals are statistical and if we perform a complete survey then we can get a better idea of actual dangers and timings.