While standing on planet Earth, it’s easy to forget that we’re sitting on a rock flying through the solar system on a path that could probably collide with other (smaller) space rocks, largely because we can’t feel it. movement.
If you ever have the urge to feel completely at the mercy of random space rocks, we highly recommend heading over to NASA’s Eyes on Asteroids website and choosing their closest approach.
NASA and other observatories track the orbits of objects found in the Solar System, paying particular attention to “near-Earth objects” (NEOs) 140 meters (460 feet) and larger that could wreak havoc if they hit The Earth. By observing their orbits, astrophysicists are able to estimate the future orbits of the objects and predict whether they potentially place them in our part of the Solar System.
These sites are rated on the Palmero scale.
“The scale compares the probability of a detected potential impact to the average risk posed by objects of the same size or larger over the years leading up to the date of the potential impact,” explains NASA’s Center for Near-Earth Object Studies. “This average risk of random effects is known as background risk. For convenience, the scale is logarithmic, so, for example, a Palermo scale value of -2 indicates that a detected potential impact event is only 1 percent as likely as a random background event occurring in subsequent years, a value of zero indicates that the single event is as threatening as the underlying hazard, and a value of +2 indicates an event that is 100 times more likely than a background impact from an object at least as large before the date of the potential impact in question.”
The sites are also given a friendlier “Torino” score of 0-10, with a score of 0 meaning the probability of an impact is zero or thereabouts and 10 meaning “a collision is certain, capable of causing a global climate catastrophe that could threaten the future of civilization as we know it, whether it affects land or ocean.” They are color coded in green, yellow and red to clarify the situation to the public.
Over the years of observing space objects, astronomers have found objects that have deviated from the green zone. However, there are a few that have made it to level 4; the highest level of the yellow zone.
“A close encounter worthy of attention from astronomers,” NASA explains about the level. “Current calculations give a 1 percent or better chance of a collision capable of devastating the region. New telescope observations will most likely lead to a shift to level 0. Attention from the public and from government officials is well-deserved if the rendezvous is less than a decade away.”
One of these objects was 99942 Apophis. After it was first discovered in 2004, observations put it at level 2 on the Turin scale. However, further observations in December of that year put it at Level 4 due to a 1.6% chance of the asteroid hitting us in 2029. Further observations ruled out a collision in 2029, as well as in 2036 and 2068. although there will still be close encounters.
There are currently no known objects with a Torino score above 0. However, there are objects that require further observations, with a Palmero score of -0.93 and -1.59, which have not received a Torino score, as possible collisions take place further more than 100 years in the future.
(29075) 1950 DA, an object 1.3 kilometers (0.81 mi) in diameter, has a score of -0.93 due to a “potentially very close” approach to Earth on March 16, 2880. This is likely to change in the coming years, as there are more observations made.
101955 Bennu (1999 RQ36) – more simply known as ‘Bennu’ – is currently at -1.59 on the Palmero scale. As far as we can tell, it will make several close approaches to the Moon and Earth. In September 2135, it is expected to pass within 0.00143 astronomical units (AU) of Earth, 1 AU being the distance between Earth and the Sun. That’s 213,925 kilometers (132,927 miles)which is quite close in terms of space.
As these asteroids orbit, more observations are made and trajectories are refined, meaning these results can go up or down. The further back in time, the greater the chance that objects’ orbits will be disrupted by close encounters with other objects (such as Earth).
So far, astronomers have been able to predict the orbits of known objects up to about 100 years into the future. The good news is that “no known asteroid larger than 140 meters in size has a significant chance of hitting Earth in the next 100 years,” according to Dr. Kelly Fast, manager of NASA’s NEO Observation Program at HQ of NASA in 2018.
In better news, a team led by Oscar Fuentes-Muñoz of the University of Colorado Boulder has gone even further, predicting the paths of larger asteroids 1,000 years into the future.
“Assessing impact risk on longer time scales is challenging as orbital uncertainties grow. To overcome this limitation, we analyze the evolution of the minimum orbit crossing distance (MOID), which limits the closest possible encounters between the asteroid and Earth,” the team explains in their paper. “The evolution of the MOID highlights NEOs that are near Earth for longer periods of time, and we propose a method to estimate the probability of a deep Earth encounter during these periods.”
Using this method, the team was able to rule out the majority of NEOs hitting our planet in the next thousand years, and can estimate the likelihood of others hitting us like a bunch of dinosaurs. The likelihood of being hit before 3,000 years seems pretty low according to the team, with the most likely object to hit us – 7482 (1994 PC1) – having only a 0.00151 percent chance of a close encounter, approaching Earth closer than the orbit of The moon.
