Hello and goodbye, asteroid 99942 Apophis. Your visit will be quick as you whip by planet Earth this week. Every time an asteroid comes close, earthlings start to wonder when they will get hit. See you when you pass by again in 2029.
The next close encounter to take seriously is an asteroid known as 2012 DA 14, which will pass quite close to Earth -- nearer than the Moon -- and perilously close to several orbiting satellites Feb. 15.
Weekly, sometimes daily, an asteroid zips close enough to the planet to show up on NASA's Near Earth Object List. The 99942 Apophis asteroid was once thought to be the one that threatened the Earth most, the one that could smash into the fragile planet.
But scientists have had enough time to study Apophis to know it isn't a serious threat.
Edward T. Lu might seem like an unlikely asteroid hunter. He's a physicist and former astronaut. For skeptics who think asteroid impacts are science fiction, he said, check what happened in Siberia in 1908.
A 330-foot meteor exploded in the atmosphere above the Tunguska River with an impact 1,000 times more powerful than the atomic bomb that detonated on Hiroshima. The force in Siberia destroyed an area the size San Francisco.
Lu now heads the non-profit B612 Foundation, a group dedicated to hunting down asteroids before they hit Earth. B612 wants to launch the first privately funded deep-space mission: Sentinel, a space telescope to orbit the sun and map the inner Solar System in search of asteroids that smash into Earth.
The goal, Lu says, is to see what's out there. Before it hits Earth.
The problem, he said, isn't the asteroids that hunters know about, but those they don't know about. "For everyone we know about, there are about 100 more we don't know about," he said. "We have to find the other 99."
To do that, Sentinel will do what no government has funded yet, a dedicated long-term search with a unique infrared space telescope constantly scanning space for the threat of asteroids, which are hunks of rock or ice, too small to be a planet, that orbit the sun.
"Once we find an asteroid," Lu said, "it is possible for us to predict its trajectory. We know the government wants to discover asteroids big enough to wipe out the planet but we also want to find those that could wipe out a city the size of New York, or Hong Kong, or Houston."
The plan is to launch Sentinel in five years on a SpaceX Falcon 9 rocket, orbit for five years and gather information about asteroids that would give governments time to take action.
What kind of action? Scientists sometimes talk about the three Ds: detect, deflect and destroy. Lu Scoffs at the notion of blowing up an asteroid in space. It creates more space debris. Deflection is much more logical.
Lu and astronaut Stan Love have come up with the concept of a Space Tug, a rocket that would launch to the same orbit as an asteroid threatening to hit the Earth, and alter the orbit by pushing in the direction of its orbital motion.
"You don't have to change much, one hundred thousandth of a mile an hour is enough, 10 years ahead of time, to cause an asteroid to miss the rendezvous with Earth," Lu said.
What government wouldn't rally to the cause of keeping an asteroid from destroying Earth? The precedent has already been set with the International Space Station, funded and built by 16 countries. Cooperating to build a rocket to save the planet would be a no-brainer, Lu said.
He spent six months on the International Space Station with its unique views of the planet, orbiting Earth every 90 minutes, seeing a planet with no borders.
He came back feeling protective of the fragile oasis. "We have been given a gift, the ability to protect our planet," he said. "We shouldn't squander it."