Updated June 01, 2013

Torino Scale

Asteroid 2011 MD came close to Earth

The asteroid 2011 MD, 10 meters in diameter was close to Earth, June 27, 2011, it passed just 12,300 miles from Earth. The asteroid 2011 MD, monitored by NASA, is a small NEO, about ten meters in diameter, barely. It was spotted by astronomers Program Lincoln Near-Earth Asteroid Research (Linear) from Socorro, in the state of New Mexico.
The number of NEOs is estimated at, 7500.
These cosmic dust are small rocky objects, with diameters ranging from several meters to tens of kilometers. Among these are about a thousand objects considered dangerous. These asteroids are classified on the Torino Scale. The asteroid 2011 MD was classified, 0 on the Torino Scale, which means that the probability of a collision is zero or practically zero. This applies to small objects such as meteors and blocks that burn in the atmosphere.

The transition from a near-Earth, occurs once every six years on average. This time it went to just 12,300 miles from Earth, June 27, 2011 to 17H (UTC).
This distance corresponds to the orbits of artificial Earth satellites, like GPS. For security reasons, astronomers working on the International Space Station (ISS), have taken shelter in the capsules of the station, to be ready to return to Earth.

Image: As shown in this simulated image, the asteroid 2011 MD (top right) is spent within the orbits of GPS satellites 31. Its distance from Earth was then only 12 300 km. Its trajectory was strongly bent by the attraction of the Earth, then left in space, continuing its travel around the Sun.

passage of the asteroid 2011 MD June 27, 2011

Risk classification of asteroid impacts

The Torino Scale was created in 1995 by Richard Binzel, a researcher at Massachusetts Institute of Technology in the department of planetary sciences.
This scale for the public, is used to classify the anticipated risks, impacts of asteroids or comets near Earth. It is graduated from 0 (no risk of collision) to 10 (certain collision and global catastrophe).
The first version of the Torino Scale (1999), was adopted in Turin, Italy, at a conference of the International Astronomical Union on NEOs. What gave it its name.
A new version was published in 2005. In a single numerical value, the Torino Scale is indicative of simplistic risk estimates for a possible collision.
This information outlines the dangerousness and likelihood of impact.
The Torino Scale is graduated from 0 to 10.
Several organizations can assign a risk value on the Torino Scale, to celestial objects, including automated systems NEODyS and Sentry.
Another scale, the scale of Palermo, for specialists, is used to classify and prioritize potential impact. It covers a range of dates of impact energies and probabilities.
The scale values less than -2, reflects events for which there is no risk, while values between -2 and 0, indicate situations that merit careful monitoring.
The scale compares the likelihood of the potential impact detected, with the risk represented means available to the objects of the same size, in the past. The average risk is called basis risk.
For convenience the scale is logarithmic, for example, the value -2 indicates that the potential impact is only 1% of the "background noise".
The background noise is the usual flow, small asteroids or meteors. The value 0 indicates that the event is just as threatening as the "background noise", and a value of 2 indicates an event that is 100 times higher than "background noise".
Reference to the scientific paper entitled "Quantifying the risks posed by potential Earth impacts" by Chesley et al. Icarus 159, 423-432 (2002).
Much of the usefulness of the Palermo Scale is its ability to carefully evaluate the risks posed by the less threatening objects, i.e. those considered to 0 in the Torino Scale.
These objects represent almost all impacts detected since the early observations.
This continuum includes both positive and negative values, it includes the time between the present and the potential impact expected, and the energy of the object and the expected probability of occurrence.
As there are many more small asteroids than large, in space, the rate will depend on the size of the asteroid.

Background noise, seen as the usual state, the status quo, and so when an object passes close to Earth, it's size that determines whether it is background noise or not. There is no practical conversion between these two scales, the Torino Scale and scale of Palermo.
The Palermo scale is continuous and depends on how many years will elapse until the potential impact. However, if an event is raised above the background noise, it will achieve a value greater than zero, both in scale and in Palermo Torino Scale.
Named Apophis 2004 MN4 (250 meters) could be the next threat. Apophis, named after the Egyptian god Apep, the "Destroyer", was discovered in June 2004, it would be the greatest threat to Earth. It measures 270 meters long and has a mass of about 27 million tones.
It should spend in 2029 to 32 000 kilometers from Earth. It crosses the orbit of the Earth, two times every 365 days. Radar observations of near-Earth asteroids show a near-Earth asteroid about six would double. Couples NEOs are made and unmade in ten million years ago.
In September 2000, the near-Earth asteroid 2000 DP107 touches the Earth at 7.2 million kilometers (about 19 times the Earth-Moon distance).
Astronomers discover a double asteroid. Already 28 August 1993, Galileo encountered the asteroid, Ida, then located at 3 AU, reveals something very surprising, the presence of the satellite flying at 100 km altitude barely named Dactyl.
Since a large number of double asteroids have been discovered: 243 Ida, 45 Eugenia, 762 Pulcova, 90 Antiope, 87 Sylvia, 1998 WW_31...
A meteorite crater more than 20 km in diameter in six is associated with another crater. Radar observations of radio telescopes of Arecibo and Goldstone, show that the asteroid 2000 DP107 is twofold, because the two bodies are 800 m and 300 m in diameter and are separated by only 2.6 km.
The density of the larger of the two bodies is only 1.7 tones per cubic meter.
This low density means that it is an aggregate of loose rock debris assembled, like a pile of stones glued by gravity.
This lack of cohesion explains their formation according to the team of J. L. Margot.
NEOs double passing near a planet, Earth or Mars undergo gravitational effects that increase their speed, the lengthening until they separate into two distinct bodies.

Image: Scale representation of the Turin, depending on the kinetic energy, calculated megatons of TNT, and the probability of impact.

asteroid 2000 DP107

Image: 2000 DP107 is the first asteroid radar-identified as a binary system (February 2000). The first is roughly spherical with a diameter of 800 meters and the second, which orbits in 1.755 days, is approximately 300 meters. NEA credit

NB: NEO 2002 NT7 was the first object was to reach a positive (higher than the ambient risk) on the scale of Palermo, with a low probability of impact in 2019. In July 2002, the value was lowered to -0.25. On August 1, 2002, asteroid 2002 NT7 was removed from the list of objects that represent a threat for the next 100 years.

Levels of the Torino Scale

No danger (White Zone)	0	The probability of a collision is zero or practically zero. Also applies to small objects such as meteors and blocks that burn in the atmosphere.
Normal (Green Zone)	1	A passage near the Earth is expected, this does not represent a hazard. The possibility of collision is very unlikely, it will probably lead to a reassignment at level 0.
Deserves attention by astronomers (Yellow Zone)	2	Passage unusual near the Earth. While meriting attention by astronomers, the actual collision is very unlikely. This will probably lead to a reassignment at level 0.
	3	The meeting deserves attention by astronomers, since the calculations were 1% or greater chance of collision. This will probably lead to a reassignment at level 0. Attention is deserved by the public if the meeting is scheduled less than 10 years.
	4

Threatening (Orange Zone)	5	The meeting represents an uncertain threat of regional devastation. Critical attention by astronomers is needed to determine with certainty whether the collision will occur. If the encounter is less than a decade, governmental contingency planning may be warranted.
	6	The encounter by a large object, still uncertain, is a serious threat of global catastrophe. Critical attention by astronomers is needed to determine with certainty whether the collision will occur. If the meeting is scheduled at least three decades, governmental contingency planning may be warranted.
	7	The encounter by a large object, still uncertain, is a threat of global catastrophe. For an anticipated threat in the century, international contingency planning is warranted.

Certain kinds of collisions (Red Zone)	8	The collision is certain, it is capable of causing localized destruction for an impact on the Earth or a tsunami if the impact is close to the coast. Such events occur on average between once per 50 years and several times a year in 1000.
	9	The collision is certain, it is able to wreak havoc with a regional impact on land or a major tsunami for an impact at sea. Such events occur between once every 10,000 years to 100,000 years.
	10	The collision is certain, it is capable of causing global climatic catastrophe that may threaten the future of civilization, whatever the impact, land or sea. Such events occur on average once every 100,000 years.