On 27 November 2015 a bright fireball hurtled towards Earth at a velocity of 50,000 km/h. The greenish streak of burning cosmic debris lit up the night sky over Kati Thanda–Lake Eyre in South Australia for a brief six seconds before disappearing from view once more. Soon, the fireball would become just one of the 84,000 meteorites estimated to hit the Earth’s surface every year.
As the outback returned to its usual tranquillity, the quiet whirr of strategically placed cameras signified the beginning of a series of events that would result in one of the most important meteorite recovery operations to date.
Expert meteorite hunter and planetary geologist Professor Phil Bland from the Western Australian School of Mines talks with Cite about what exactly is involved in tracking and recovering a meteorite.
Step 1: Do the groundwork
Meteorites may have their origins in space, but the foundations for tracking them are best laid on the ground. On that November eve, an intelligent camera network was the key component in a bold mission to track and recover a meteorite.
“Meteorites are very rare rocks that tell us a lot about the beginning of the Solar System, as they’ve not really been altered since before planets formed,” explains Professor Phil Bland, the man behind the operation. “The problem is, we don’t know where any of them come from.”
In 2012, Professor Bland and his team from Curtin University began work on a prototype for an intelligent mechanical observatory capable of capturing a meteorite’s descent through the Earth’s atmosphere.
Comprising a DSLR camera, weatherproof housing and intelligent software, the observatory offers a simple and cheap (A$8,000) solution to tracking meteorites.
Now, the number of observatories has been scaled up, with 32 located across remote Western and South Australia. This is the Desert Fireball Network (DFN).
Each night, the DFN automatically generates a list of observed fireballs, most of which vaporise before ever hitting the ground. The night of 27 November was no different.
“We see fireballs all the time, so the lists can be quite long,” Professor Bland explains. “It took us a few days to realise that we had observed a big one – and that meant there was probably a rock on the ground. It was then that everything clicked into action.”
Step 2: Piece together the data jigsaw puzzle
Tracking an object punching through the Earth’s atmosphere at tens of kilometres a second isn’t easy, plus there are distortions in the camera lens that have to be accounted for.
“We looked at the information from each different camera to triangulate the exact trajectory of the fireball,” Professor Bland says. “One of my PhD students has created a model that uses advanced tracking algorithms to work out how quickly a meteorite is decelerating in the atmosphere, and that gives us an idea of the mass of it.”
The team tracked the meteorite from an altitude of 85 km as it descended through the atmosphere. But at about 18 km above the Earth’s surface, the fireball went dark.
“When the light went out, we had to use an advanced climate model to work out how the wind was blowing the rock off course,” he says. “At that point, we finally had an idea of where it was going to be.”
Step 3: Combine theory with observation
But data analysis can only get you so far. In this case, the predictive modelling worked out the final location to be somewhere along a 2 km fall line in the middle of the mainly dry Kati Thanda–Lake Eyre.
With an approximate location in mind, the team organised a scouting mission.
“We sent out a couple of guys to get on a little spotter plane to get a first look,” says Professor Bland. “They saw a feature on the lake that looked like where it might have hit. Now, we just had to figure out how to get there.”
With a visual on a possible impact site, combined with the data modelling from the DFN, it was starting to look like the real deal. This could be the first meteorite that was accurately tracked and recovered with a simple, low-cost camera network. But Professor Bland remained cautious.
“Really, you don’t know whether the technology is going to work,” he says. “You hope it is, you tick every single box you can think of – but at the end of the day, nature can have a way of tripping you up.”
Step 4: Get your hands dirty
“Unfortunately, between the scouting mission and us getting out there, there was a lot of rain and part of the lake had filled up,” Professor Bland says.
It had been two weeks. With people, accommodation and transport to organise – and across the Christmas period no less – the only part that went smoothly was getting permission to search the lake from the local Arabana people.
“They were amazing: the lawyer for the Aboriginal corporation got in touch with them, and literally the next day they’d given us consent to go out on the lake,” he recounts. “Two of their people, Dean Stewart and Dave Strangway, even came with us as guides, which was a huge help.”
On 29 December, the team finally arrived at the lake. But two days later, they still hadn’t found the meteorite. To make matters worse, the forecast showed heavy rain. The clock was ticking.
“On the last day of our mission, I was actually about as stressed as I’ve been on a field trip. Professor Bland recalls.
Knowing this would be their last chance to recover the meteorite before the rain wiped all trace of it away forever, the team organised a spotter plane to search from above.
Meanwhile, Professor Bland and one of his PhD students jumped on the quad bikes to continue the search on the ground. But a light drizzle turned into heavier rain, and forced them to pull part-way off the lake to avoid some of the more serious mud until the rain stopped.
“It was really touch and go,” he says.
Suddenly, the aerial spotters radioed in.
“The guys said, we’ve seen it! We’ve seen it!“ He pauses, “but then they lost it again.”
With time against them, he couldn’t wait for aerial confirmation. Leaving his bike, he headed out on foot to where the spotters had first radioed in.
“I was running through the mud, which was really knackering, until finally I saw the little impact crater – but you’re still not sure,” he confides. “You’ve got to have an awful lot of faith in the analysis to even get to this point, and it’s impossible really to do that without any element of doubt in your mind.”
Without any equipment nearby, he dug with his bare hands. He didn’t know it, but the meteorite’s impact had buried it half a metre deep in the mud. With adrenaline coursing through his system, he continued to rip out the thick clay, shredding tendons in his hands as he went.
“Finally, my fingers touched it at the bottom of this dirty, great hole,” he recalls, “and I knew that all of those little pieces in the puzzle had clicked into place.”
What happens now?
The love-heart shaped rock is now undergoing analysis to determine what it’s comprised of and how long ago it broke off from its parent asteroid.
The meteorite’s orbit has already been roughly tracked back to the main Asteroid Belt, located between Mars and Jupiter.
“What will be really exciting is when we really get into the detail of that orbit and run the clockwork Solar System backwards in time to see if it matches up with a specific asteroid,” Professor Bland says.
“If our network can continue getting samples of asteroids from down here on Earth, then it becomes a really cheap way of getting data that can help us determine how our Solar System was formed.
“And maybe, it will even begin to answer some questions about the formation and creation of life on Earth.”
The love-heart-shaped meteorite …
- is about 4.565 million years old, about 20 million years older than Earth.
- is probably part of an asteroid that was broken up about tens of millions of years ago.
- entered the Earth’s atmosphere weighing about 80 kg, but only weighed 1.7 kg by the time it hit the surface.
- is a chrondite, or stony meteorite – one of the most common types.
Which space rock is which?
An asteroid is a rocky object that’s smaller than a planet and orbits the Sun.
A meteoroid is a fragment of an asteroid, comet or planet that is travelling in space.
A meteor is a rocky object that burns and vaporises upon entry into the Earth’s atmosphere.
A meteorite is a piece of metal or rock that survives the meteoric state and impacts upon the Earth’s surface.
Did you know?
Of the 50,000 meteorites held in museums, we only know accurate orbits for 20.