Meteorite hunters in Florida have found six space rocks associated with a rare daytime fireball that streaked through the Sunshine State's skies on Jan. 24.
The newfound meteorite assemblage was the sixth recorded from Florida, and the first one linked to a fireball observed by witnesses, experts said. (The other meteorites were uncovered beneath layers of Earth long after they fell.) You can see photos of their meteorite hunt here.
"Meteorites are kind of magical," Marc Fries, a meteorite expert at NASA's Johnson Space Center in Houston, told Space.com. "Your average meteorite is about 4 and a half billion years old. It's the oldest thing you'll ever get to interact with one to one ... It’s incredible."[How to Find a Meteorite in 5 Steps]
Fries regularly keeps his eye on the American Meteor Society’s (AMS) home page as well as social media, with the hope of hearing about a recent streak in the sky or even an unexplained sonic boom.
Although fireballs occur every day, daytime fireballs tend to get scientists really excited. The fact that they're so bright that they can be seen despite the sun's glare means that the objects that cause them are likely to be at least the size of a minivan, and some pieces therefore have a good chance of reaching the ground.
So after hearing rumors that a daytime fireball streaked across Florida's sunny skies around 10:30 a.m. local time on Jan. 24, Fries immediately called Mike Hankey, who's in charge of collecting reports on the AMS website and computing trajectories of meteors' paths. While Hankey was parsing through 80 reports from eyewitness events of the fall, Fries himself was examining radar data.
Radar data is especially useful for meteorologists, because it spotlights rain and snow. But radar instruments can also detect other falling objects — meteorites.
"They're decelerating all the way down to the ground," Fries said. "So they're kind of like rifle bullets — they leave a turbulent wake behind them."
That signature can be directly spotted in the radar data, he added. To boot, radar has a high spatial resolution, allowing Fries and other researchers to compute almost exactly where each meteorite should have landed.
Fries and Hankey were working to pinpoint the meteorite's touchdown site as quickly as possible. When Hankey shot Fries an email with the final location, the latter responded quickly with "SPOT-ON BULLSEYE!" Hankey’s computed trajectory perfectly intersected with the meteorite cloud Fries had found. They both pointed toward a swamp surrounded by pine forests — not the ideal hunting grounds.
Nonetheless, news of the fall spread throughout the meteorite community like wildfire. Within five days of the fall, Hankey drove from New York to Florida's Osceola National Forest, joining four others who were eager to begin the search.
"In the first few days you want to go for low-hanging fruit," Hankey told Space.com. So the team scoured dirt roads and sandy paths — anywhere a black space rock might be easy to spot.
The first find came on the second day of searching. Hankey, while walking along a sandy road, paused to stretch, and his eye caught a shimmering black stone against the dead grass and sand.
"For the first one I found, I pretty much knew as soon as I saw it," Hankey said. It’s hard to miss certain meteorite features, like their rounded shape and surprising weight, he added. A magnet, too, will stick to a meteorite. [When Space Attacks: The 6 Craziest Meteorite Impacts]
Save for the euphoria of a find, meteorite hunts can be "really boring and monotonous in a lot of ways," Fries said.
After searching for low-hanging fruit, hunters often grid areas, walking back and forth for days to cover all the possible ground. And it can be very tough to find meteorites in rough and complex terrain — such as a forest or swamp.
In the Florida hunt, the team found four meteorites within the first two days. They searched fruitlessly for another six days, found a whopping 1.76-lb. (800 grams) stone on the seventh day, hunted another full week without luck and then turned up one final meteorite on their last day. Over the course of three weeks, four to five hunters had found a total of six stones.
And that’s only a small percentage of the potential finds, Hankey said.
"We didn't even hunt 1 percent of the square mile of this field, because we couldn't, and we found six stones," he said. "So you figure 6 times 99 is nearly 600" missed meteorites, he added. And by this summer, those rocks will be swallowed by the Earth, likely lost forever.
Even with the prospects low, meteorite hunters think a single find is well worth the extensive effort. And Fries loves the history these space rocks carry.
To truly grasp that history, Fries suggests that "you stretch your arms all the way out. Let's say that 4 and a half billion years — the age of these meteorites — is the distance from one fingertip to the other. Then you can take a nail file and scratch it once on the nail of your middle finger, and you've just erased all of recorded human history. But the meteorite has been there for the entire span of 4 and a half billion years. And you get to be the first person to ever interact with it. And that's just incredible."