Saturday is Asteroid Day, an annual, global educational event aimed at learning more about the hazard that nearby asteroids pose to Earth and our civilization, and marshaling support for the search and deflection technologies we need to protect our planet. Many thousands will gather around the world this weekend to hear the latest science on the asteroid hazard, and what we can do to prevent a future damaging impact. (For more visit AsteroidDay.org)
Asteroid Day falls on June 30, the anniversary of the 1908 asteroid impact in Tunguska, Siberia – the largest in recorded human history. That 3 – to 5 – megaton blast above the conifer forest flattened about 800 square miles of trees; a similar airburst today over a modern city would cause severe destruction and death.
The history of impacts on Earth, and our studies of near-Earth asteroids, tells us with certainty that our planet will be struck again – unless we act together to head off hazardous asteroids.
This year’s Asteroid Day is the fourth such global event. The astronauts’ international professional society, the Association of Space Explorers, proposed to the United Nations in 2016 that Asteroid Day be recognized as a global educational event. The General Assembly approved their suggestion later that same year.
Fifty years ago, the first astronauts to orbit and later walk on the moon saw with their own eyes a world blasted with the countless scars – craters – of asteroid and comet impacts.
Such craters are familiar landmarks for my Earth-orbiting colleagues; I saw a dozen or more on my four shuttle missions. These scars show that our world suffers from the same 4.5 – billion – year – old cosmic bombardment process. Geologists now count about 190 craters scattered across continents and seafloors.
A Global Hazard
Protecting Earth from future impacts is a shared responsibility: all of us, in every country, are at risk from this cosmic rain.
The Association of Space Explorers continues to contribute to United Nations discussions of how to find asteroids and prevent an impact. The U.N. even adopted, in 2013, several of our suggestions on how to share asteroid sightings and warnings and make cooperative efforts to test deflection methods.
More importantly, the world’s space agencies, with active NASA leadership, have advanced the science of asteroid detection and the identification of technologies that can nudge a rogue asteroid from its collision path with Earth. These conversations have led to a proposed deflection demonstration mission, called DART, that if funded will slam into a harmless asteroid in 2022 and change its orbital path. The results of that bullet shot, observed by Earth astronomers and a proposed European observer craft, will tell us if we’re ready to use this “kinetic impact” method on a future threatening asteroid. Other methods, like the gravity tractor and directed energy beams, should undergo their own in-space tests, too.
Defending Earth Together
NASA and its partner space agencies have cataloged over 18,000 near–Earth asteroids, and none have yet been found to pose a future threat to Earth. But in the past decade, NASA–funded searches have discovered three small asteroids -- too tiny to reach the ground -- and predicted their harmless incineration in the atmosphere. These impacts were observed by satellites and ground observers (from my perch on the space shuttle, I was fascinated to see meteoroids burn up in the atmosphere below me).
In 2013, a 60–foot asteroid plunged into Earth’s atmosphere without warning over the Russian city of Chelyabinsk. The asteroid’s disintegration generated a half-megaton shock wave that blew out windows, damaged roofs, and sent more than a thousand to the hospital. No one was killed.
Chelyabinsk’s unexpected arrival reminded us of the need to increase the pace and sensitivity of our asteroid search. A modest infrared telescope, comparable in cost to a Mars orbiter mission, would find a large fraction of objects, 140 meters and larger, capable of causing regional destruction on our planet. A collision with one of these objects could devastate, for example, Washington, D.C. and five or six surrounding states. Congress directed NASA to perform this search back in 2005 but didn’t provide the funds. We should encourage our representatives to give NASA the funds to fly the proposed NEOCam telescope within the next five years.
NASA also needs the money to build and launch its DART deflection demonstrator craft, aiming to measurably nudge asteroid Didymos – B in October 2022.
Asteroid Day is a reminder to us to nudge lawmakers to fully fund this important test. Because of the worldwide hazard posed by asteroids, I hope NASA will be joined by its partner space agencies in paying for these two planetary defense missions.
The more asteroids we discover, and the more we learn about them (through, for example, the Japanese and U.S. asteroid science missions arriving this summer at two target asteroids), the more rapidly we can employ these objects in our exploration efforts. Water, metals, and even rocks and dust from asteroids can be used to increase the safety of Mars–bound astronauts, lower the mission cost, and grow a vibrant asteroid mining economy in and around the Earth– Moon system.
A Preventable Disaster
We now possess the space technologies needed to identify and stop the threat from dangerous asteroids.
We are slowly building a better ability to find dangerous asteroids, and our computers can project known asteroid orbits a century into the future to predict possible impacts.
NASA and its partner agencies are also planning actual space tests that will show us how to change the orbits of near–Earth asteroids and ensure we can divert those that might have deadly appointments with Earth. But these efforts take money, and in the interests of public safety, we should fund them promptly and fully. (The NEOCam search mission, for example, would total much less than one percent of NASA’s budget over ten years).
We already have many answers to our questions about asteroids. However, the most important one is still unanswered: Do we have the will to act together to defend our planet? If we answer yes, then humanity will survive and spread rapidly across the solar system. If we fail to act, we are certain to suffer the fate of the dinosaurs.