Since the first known asteroids were discovered around the beginning of the 19th Century, a great deal of information and tracking has developed in the last few decades—along with the awareness of a possible devastating impact on Earth. “We probably should have always been worried about this. It took the last 25 to 30 years to see this as a real possibility,” says John Conrad, a NASA JPL ambassador and retired astronautical engineer who is a frequent speaker to astronomy clubs and students, as well as at DMNH’s Member’s Preview Party for Great Balls of Fire.
The first direct observation of a comet hitting a planet was in July 1994, when Comet Shoemaker-Levy 9 broke apart and collided with Jupiter. “It got people’s attention,” Conrad said. The collision was on the scale of the impact that likely ended the reign of dinosaurs on Earth.
Fortunately, the interest in Comet Shoemaker-Levy 9 resulted in an increase in funding for programs to find and track Near Earth Objects. In the last few decades, the knowledge of where these comets and asteroids are has increased exponentially. NASA’s NEO program office has been in place since 1998 and manages information from other programs such as the National Science Foundation to detect, track and characterize potentially hazardous asteroids and comets that could approach the Earth. “NASA both manages and coordinates many great people, surveillance and analysis programs, using a number of large ground-based and space-based telescopes to create and update a huge NEO knowledge base,” Conrad says.
Well over 10,000 NEOs have been found and are routinely tracked in their solar orbits. Once the individual object’s orbit is understood, it does not have to be rediscovered because the orbits can be predicted and then tracked by instruments. “You can always know by your predictions where they will relative to Earth’s path. Predicted close approaches are the most interesting and are prominently featured in the NASA NEO webpages. “Bigger ones are easier to see and most were found earlier,” he said. But more than 1,500 of all sizes are added to the database each year.
While the Earth is often hit by smaller meteorites, NASA’s NEO program is not predicting a larger impact for the foreseeable future, certainly the next few decades. “If there was something big coming soon, we’d know that now,” Conrad says.
That doesn’t mean a catastrophic impact couldn’t ever happen, though. NASA’s Planetary Defense program was created to “encompass all the capabilities needed to detect the possibility and warn of potential asteroid or comet impacts with Earth, and then either prevent them or mitigate their possible effects,” according to NASA’s website. This includes finding and tracking NEOs, determining possible impact events, developing a warning system and determining how to mitigate potential impact.
Interested in learning more?
Visit the NASA Near Earth Object program online:
For information on NASA’s Planetary Defense initiative, visit: www.nasa.gov/planetarydefense
To learn about NASA’s Asteroid and Comet Watch, visit: