This article was originally published on The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.
At sunrise on February 15, 2013, an extremely bright and otherworldly object roamed the sky over Russia before it exploded over 97,000 feet above the Earth's surface. The resulting explosion damaged thousands of buildings and injured nearly 1,500 people in Chelyabinsk and the surrounding area. While this sounds like the first scene of a science-fiction movie, this intruder was not an alien spaceship attacking humanity, but a 20-meter-wide asteroid that collided with Earth.
What's worrisome was that no one had any idea that this 20-meter asteroid existed until it entered the Earth's atmosphere that morning.
As an astronomer, I study objects in the sky that change in brightness over short time scales ̵
Near-Earth Objects  A meteor is a matter that penetrates the earth's atmosphere. Before the Chelyabinsk meteor experienced its downfall on Earth, it circled our sun as an asteroid. It is believed that these rocky objects are usually confined to the asteroid belt between Mars and Jupiter. However, there are many asteroids throughout the solar system. Some, such as the Chelyabinsk meteor, are known as near-Earth objects (NEOs).
The Chelyabinsk meteor probably came from a group of NEOs called Apollo asteroids, named after the asteroid 1862 Apollo. There are more than 1,600 known Apollo asteroids registered in the small body JPL database, whose orbits cross Earth's path. They are tall enough (over 140 meters) to be considered as potentially dangerous asteroids (PHAs) due to a collision with Earth, the region hit would be devastated.
The scars of these past collisions are prominent on the moon, but the earth also bears the mark of such impacts. The Chicxulub Crater on Mexico's Yucatan Peninsula was created by the Chicxulub asteroid, which brought the dinosaurs to extinction. The Barringer Crater in Arizona is only 50,000 years old. The question is not whether a dangerously large asteroid will collide with the earth, but when …
In search of threats
The US government takes the threat of an asteroid collision seriously. In Section 321 of the NASA Authorization Act of 2005, Congress called on NASA to develop a NEO search program. NASA's mission was to identify 90 percent of all NEOs over 140 meters in diameter. Currently, they estimate that three quarters of the 25,000 PHAs still need to be found.
To achieve this goal, an international team of hundreds of scientists, including myself, completes the construction of the Large Synoptic Survey Telescope (LSST). in Chile, which will be an important tool to point out PHAs.
With significant financial support from the US National Science Foundation, LSST will seek out the same skyline in its 10-year mission PHAs hourly distance to objects that have changed their position. Anything moving in an hour must be so close that it is in our solar system. Teams led by researchers from the University of Washington and JPL have both produced simulations demonstrating that LSST alone will be able to find approximately 65 percent of the PHAs. When we combine LSST data with other astronomical surveys such as Pan-STARRS and the Catalina Sky Survey, we believe we can help detect 90 percent of the potentially dangerous asteroids.
Preparing to Prevent a Disaster
Both the Earth and these asteroids orbit the Sun only in different ways. The more observations made by a given asteroid, the more accurately its orbit can be mapped and predicted. The biggest priority then is to find asteroids that could collide with Earth in the future.
If an asteroid is on a collision course for hours or days before it occurs, the Earth will not have many options. It's like a car that suddenly pulls out in front of you. There is little that you can do. However, if we find these asteroids years or decades before a potential collision, we can use spaceships to push the asteroid enough to change its path so that it and the earth do not collide.
But easier said than done, and currently no one really knows how well an asteroid can be diverted. There have been several proposals for missions by NASA and the European Space Agency to do so, but so far they have not passed through the early stages of mission development.
The B612 Foundation, a private nonprofit group, is also trying to raise money privately for a mission to divert an asteroid, and they may be the first to try it if the government's space programs fail to do so. Squeezing an asteroid sounds like a weird thing, but if we find an asteroid on a collision course with Earth someday, it may be this knowledge that will save humanity.
Michael B. Lund, Post-Doctoral Student, Department of Physics and Astronomy, Vanderbilt University
This article was originally published on The Conversation. Read the original article. Follow all the questions and debates of Expert Voices – and become part of the discussion – on Facebook, Twitter and Google +. The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on Space.com.