If you were looking up at the right place at the right time 100 years ago next Saturday, you might have seen something very special.
On Feb. 9, 1913, the night lit up unexpectedly as dozens of brilliant fireballs blazed across the sky in a slow and stately procession. The rare spectacle was witnessed along a narrow track that stretched from central Alberta to the south Atlantic. In Toronto, The Globe office was flooded with reports of "a meteoric performance of stupendous dimensions," a front-page story relates. Professional astronomers were no less excited – or puzzled.
Long before the space age, people had no sense of what a satellite looks like when it burns up in the atmosphere. Yet scientists say that is most likely what witnesses saw that night – not a manmade Sputnik but a tiny, natural satellite of the Earth, a "minimoon" in the throes of a fiery demise.
The curious event, unlike anything seen since, took on new relevance this week when scientists at a special NASA workshop made their case for a mission to find more unseen minimoons buzzing around our planet. Once spotted, they say, such objects could be reeled in and brought down to Earth, where they could unlock a treasure trove of secrets about our planet's origins.
"My ultimate dream is to go get them," said Robert Jedicke, a Canadian astrophysicist at the University of Hawaii's Institute for Astronomy in Hilo, who made the presentation to NASA on Tuesday. "These are the Rosetta Stones of the solar system."
To fulfill his dream, Dr. Jedicke hopes to leverage an unexpected opportunity. Last year, the U.S. National Reconnaissance Office, part of the Pentagon's intelligence-gathering apparatus, gave NASA the mirrors and related hardware to build two large space observatories, each the size of the Hubble Space Telescope. Thought to have been intended for spy satellites that never flew, the optics are suddenly free for civilian duty. It's now up to the space agency to figure out a good use for the giant mirrors and then pony up the cash to complete and launch them.
Dr. Jedicke and his colleagues were among those selected to pitch their proposals at the workshop, held at NASA's Marshall Space Flight Center in Huntsville, Ala. Their idea is to place one of the former spy scopes at a point about 1.5 million kilometres from Earth, where it can look back and spot minimoons.
"They should be out there," said Peter Brown, a planetary scientist at the University of Western Ontario and a member of the proposal team. Dr. Brown operates an automated meteor observing system that could, in principle, spot a minimoon passing overhead, but he says a space-based system is required to reveal the retinue of objects coming and going in near-Earth space.
Scientific interest in minimoons stems from the fact that the elusive objects cannot have formed around Earth, but must instead have journeyed here from the asteroid belt, a zone of rocky fragments located between the orbits of Mars and Jupiter. Asteroids are the remnants of the raw materials that fed the formation of Earth and other planets some 4 1/2-billion years ago. Robotic missions to visit the asteroids and return small samples are high on the wish list of scientists who study the solar system's cosmic beginnings.
Dr. Jedicke and others envision bypassing a long journey to the asteroid belt for a handful of rocks and instead snaring entire boulders that have temporarily drifted into Earth's neighbourhood and become minimoons. "The asteroids come to us," he said. "We can sample the solar system from our own backyard."
A 2012 study produced by researchers at NASA's Jet Propulsion Lab in Pasadena and the California Institute of Technology proposes a garbage-truck-like craft that could envelop a space rock as large as seven metres across, with a mass of 500 tonnes. But most minimoons would be more manageable. Computer simulations suggest that at any given time there are about two objects the size of a dishwasher in orbit around Earth, and perhaps a dozen the size of a microwave oven. Most will eventually break free again and drift back into an orbit aroud the Sun, but about 1 per cent will enter Earth's atmosphere, potentially fragmenting and burning up in spectacular fashion like the fireball procession of 1913.
While not unique in history, that event "is by far the most spectacular ever recorded," said Donald Olson, an astronomer at Texas State University-San Marcos. Together with Steven Hutcheon, a researcher with the Astronomical Association of Queensland, Australia, he recently brought to light previously unknown sightings of the event made by ships at sea off the coast of Brazil. The findings, published this month in Sky and Telescope magazine, extend the track of the procession south of the equator and lend weight to the theory that the 1913 event was the breakup of a minimoon.
If Dr. Jedicke's telescope proposal is successful, the next such light show may not be as unexpected.