Two asteroids pass by the Earth

Two small asteroids are going to pass very near to our planet on Wednesday 8 September. An event which could actually be quite commonplace!

 

Orbits of 2010 RX30 and 2010 RF12, the two small asteroids that are to pass by the Earth today, Wednesday 8 September 2010. Credit: JPL-NASA

We would make it clear straightaway that these two objects are in no way a threat to us. First of all, their trajectory has been calculated with sufficient precision to rule out any risk of impact, and secondly, they are too small to cause any damage on the ground. This double passing does show however why the study of Near-Earth asteroids (those that cut across or come close to the Earth’s orbit) is more and more becoming a space exploration priority.

2010 RX30 and 2010 RF12: two asteroids like so many others...
The two “wandering stones” that we are talking about were detected on 5 September 2010 by the Catalina Sky Survey, a programme for detecting potentially dangerous asteroids that unites 3 observatories: two in Arizona, United States and another one in Siding Spring, Australia. The different observations made have enabled astronomers to determine the size and orbit of the two objects referenced 2010 RX30 and 2010 RF12. The first is between 10 and 20 m wide and, at the closest point, will pass 248,000 km from the Earth today, Wednesday 8 September at 09:51 UT (Universal Time, 11:51 French time). The second is much smaller (6 to 14 m in diameter), but should pass much closer to our planet at a distance of 79,000 km on the same day at 21:12 UT (23:12 French time).

Another diagram of today’s two near trajectories shown from a different angle. Credit: JPL-NASA/traduction Enjoy Space

These distances mean that the two small Near-Earth asteroids will briefly therefore pass closer to us than the Moon which orbits at a distance of about 385,000 km. The event initially seems to be unusual because 2010 RX30 and 2010 RF12 pass so near to us. But only initially! This is because astronomers estimate that these two Near-Earth asteroids are part of the large family of asteroids measuring a dozen or so metres in diameter... a family which could have more than 50 million members. More astonishing still, an asteroid of this type passes by our blue planet within the Earth-Moon distance every day. Clearly, 2010 RX30 and 2010 RF12 are nothing out of the ordinary! Luckily, they are too small to cause any damage on the ground: should they happen to enter our atmosphere, they are predominantly destroyed and only a few fragments reach the ground. An entry into the atmosphere of this sort (that is to say of objects measuring a dozen or so meters in diameter) happens about once every ten years.

One of the Catalina Sky Survey telescopes that scan the sky, looking for objects that could potentially be dangerous for our planet and our civilisation. Credit: Catalina Sky Survey

Survey and protect
This apparently commonplace event does not however satisfy astronomers and, over the years, budgets have been increased more and more in order to set up a system for surveying the sky with a view to referencing Near-Earth objects (whether they are asteroids or comets) and detecting all those that could one day collide with the Earth as soon as possible. However, the strategies to be applied in the event of a threat remain vague. Some put forward violent methods such as the use of thermonuclear explosions in order to divert the threatening object from its trajectory, whereas others advocate the implementation of more “gentle” solutions (the gravity tractor where a spacecraft placed in front of the asteroid would progressively change its path) which should provide more accurate results (to find out more, read this Enjoy Space feature).

Several asteroids observed using space probes. From left to right: Eros (34 km wide) in 2000 by NEAR, Itokawa (535 m wide) by Hayabusa in 2005 and Lutetia (132 km wide) by Rosetta in 2010. Objects that vary greatly as confirmed by other studies (see this Enjoy Space news). Credit: NASA/JAXA/ESA/page setup Enjoy Space

Several space agencies are taking a very serious look at this subject. And although there is a difference of opinion concerning the deflection methods, unanimity is the order of the day when it comes to concluding that we do not know enough about these objects. Robotic space missions which have either explored or flown by asteroids have moreover shown how varied they are. This explains why the study of these small objects using probes, in addition to a scientific interest linked to understanding the formation of the solar system, has once again become a major part of the space programmes. And in this respect, it is worthy of note that at the beginning of the year, President Barack Obama cancelled the return to the Moon requested of NASA by his predecessor in order to give preference to the preparation of a manned mission to a Near-Earth asteroid before 2025.

President Barack Obama wants NASA to send astronauts to a Near-Earth asteroid by 2025. A first in the realm of human space flights. Credit: NASA

Published on 8 September 2010