Scientists are on the lookout for asteroids that could pose a danger to Earth but which could also hold the key to understanding life’s origin.
A frame grab from a dashboard camera shows a meteor over Chelyabinsk, about 930 miles east of Moscow, Russia, 15 February 2013. (AP Photo/AP Video)
Have you ever made a wish on a falling star as it sparkled through the night sky?
Those flashes of light are caused by space rocks — usually the size of a pebble. Known as meteors when entering Earth’s atmosphere and meteorites when they land, most space material is microscopic, virtually cosmic dust.
Yet every year our planet is bombarded by an estimated 40,000 tonnes of material originating from asteroids. Mostly it falls to the surface unnoticed or into the oceans, which are 71% of the Earth’s surface.
But 65 million years ago, the dinosaurs had a very bad day when a space rock the size of a city hit Earth. An asteroid 10 kilometers in diameter created a 185-kilometer crater in modern-day Yucatan Peninsula, Mexico. Known as the Chicxulub Impact, it triggered a global cataclysm of fire, floods and years of darkened skies that caused the abrupt end of the Cretaceous period, when dinosaurs dominated the earth.
So, what are these rocks that flash through the night sky when they are tiny, and which can trigger the extinction of species when they are massive?
Protecting Earth and probing life’s origins
Asteroids are ancient space rubble, the rocky remnants left over from the formation of our solar system. Most asteroids orbit the Sun between Mars and Jupiter, known as the asteroid belt. Scientists have gained these insights by studying asteroids and meteorites that fell to Earth as long as 4.5 billion years ago.
The larger asteroids, such as Vesta, which is 530 kilometers in diameter, are named. To date, scientists have identified just more than one million asteroids.
Space scientists try to keep tabs on all asteroids longer than 10 meters in diameter. “The dinosaurs couldn’t, but we humans have the benefit of knowledge and science on our side,” said British astrophysicist Dr. Brian May, who many remember as the lead guitarist of the rock group Queen.
May and Apollo 9 astronaut Rusty Schweickart founded Asteroid Day, which is marked every June 30th and sanctioned by the United Nations as a day of public awareness about asteroid impacts.
Schweickart believes we must know and track every significant asteroid in order to “develop a dynamic map of the inner solar system.” That’s so we can protect the Earth and explore asteroids in search of the answer to what he calls “the big question” of whether life predates the solar system or began on Earth.
Like the former Apollo astronaut, the U.S. National Aeronautics and Space Administration (NASA) takes asteroids seriously. Using ground-based telescopes and spacecraft, the government agency identifies Near Earth Objects (NEOs) that may pose a hazard to Earth. A new asteroid-hunting spacecraft, the NEO Surveyor, was approved earlier this month.
Defense systems will shield Earth from threatening asteroids.
Happily, NASA says there are no known impact threats to Earth for the next century. By then, planetary defense systems, involving various ways to fend off threatening asteroids, will have been perfected.
Spacecraft from several nations have visited some of the larger asteroids and even brought samples back to Earth. The concept of mining asteroids for space travel is being actively researched, and asteroids may turn out to be useful material for future space travellers.
Would you like a souvenir from the birth of our solar system?
If you see a meteorite fall but can’t find it, you could join a scientific expedition to Antarctica. That’s where up to 40,000 meteorites, easy to spot on ice and accounting for around two thirds of known meteorites, have been recovered. Or you could head to the Sahara, where the arid climate preserves them.
There is a brisk trade by local people who find and sell meteorites to collectors. Even ancient Egyptians prized meteorite metal, although we don’t know if they understood its extraterrestrial origins. A knife found in King Tutankhamun’s tomb in 1925 has been identified as meteorite iron.
You might be very lucky and find an asteroid from the Moon or even Mars. A rock that hits Mars or the Moon can bounce off the surface and embark on a new space journey. There are 400 known lunar meteorites and around 160 Martian meteorites on Earth.
Amazingly, a Martian meteorite from the collection of London’s Natural History Museum is now back on Mars. Known as SaU 008, it’s helping calibrate the rock identification laser on NASA’s Mars Perseverance Rover, which landed on the red planet in February, making it the only meteorite that has returned home.
It may sound like science fiction, but think of that when you next gaze at the night sky.
Three questions to consider:
- What’s the difference between an asteroid and a meteorite?
- What is International Asteroid Day?
- If there is no threat from asteroids for the next century, why spend money tracking them?
Tira Shubart is a freelance journalist and media trainer based in London. She has produced television news and trained journalists across four continents for international broadcasters, including BBC News, Canadian Broadcasting Corporation and Al Jazeera, over several decades.