It’s not easy convincing the world you’ve found aliens. But that’s what one British professor says he’s done, over and over again. His latest proof, he tells me, is his strongest yet. Should we take him seriously?

In fall of 2013, Milton Wainwright, a researcher at the University of Sheffield in the United Kingdom, made international headlines when he claimed that microorganisms he found in the stratosphere were not of this world. The organisms are believed to come from a class of algae called diatoms, were collected roughly 16 miles above the Earth’s surface using a balloon, and, according to Wainwright, have been raining down on the Earth, carried by meteorites, for perhaps many millennia.

The story goes something like this. Wainwright found these organisms 16 miles above Earth. He says that’s too high for any life from Earth to float in a jet stream, and he says the organisms are too heavy to get up that high without a recent volcanic blast. He says there were no recent blasts before the expedition, and, furthermore, the collection apparatus showed tiny divots in it, suggesting that these organisms hit the tin with some sort of speed. His conclusion, then, is that these organisms came from space.

“This we think is a deflated balloon-like biological entity. Perhaps when inflated, it aided flotation in the atmosphere or sea of another world,” Wainwright said. Image: Milton Wainwright

While the we-found-aliens headline played well among the tabloids of the world, Wainwright’s discovery was unceremoniously tossed aside by science journalists.

“The methodology was sloppy, the conclusions were not at all supported by the evidence, and heck,he hadn’t even established that the rocks they found were in fact meteorites!,” Slate’s Phil Plait wrote.

“All the time when you walk outside, you are being pelted with organisms that come from space”

Plait isn’t wrong—the original evidence was flimsy, and there was no shortage of scientists standing in line ready to say so. But few said he was outright wrong. Many who spoke out at the time said that, while there wasn’t enough evidence to call these things aliens, panspermia—the idea that alien life may regularly travel to Earth from space—isn’t entirely nuts.

Now, Wainwright has made another claim. He says he has found these organisms 25 miles above the Earth, that they test positive for DNA, and that they have masses that are “six times bigger than the size limit of a particle which can be elevated from Earth to this height, even following a violent volcanic eruption.”

Wainwright announced the find in an email to some of his students at Sheffield, who naturally, posted the thing on Reddit.

DNA-positive potential alien. Image: Milton Wainwright

So, I called Wainwright to hear what he has to say. Let’s make it clear now—I have no idea if Wainwright has, indeed, found aliens. His first paper was published in a somewhat dubious journal, and it certainly didn’t contain “extraordinary proof” of alien life, which is what one NASA scientist said he would need in order to take Wainwright’s claims seriously.

“These organisms are biological, have a definite structure, and are not related to organisms on Earth. We sent balloons and a sampler and found no pollen or grass, nothing up there to contaminate, it was completely pristine,” Wainwright told me. “There are impact events on the sampler. They make craters on the sampler—if they come up from Earth, they would be coming against gravity.”

“For these reasons, we think they are coming from space,” he added. “All the time when you walk outside, you are being pelted with organisms that come from space.”

Wainwright says his newest paper has been accepted in an “international astrobiology journal” but hasn’t said which one and hasn’t said when the new findings will be published. He seemed taken aback when I emailed him about it, and wasn’t quite ready to discuss the new findings, but agreed to talk because the email was already on the internet.

Wainwright’s students preparing a balloon to go to the stratosphere. Image: Milton Wainwright

Take this paragraph with many grains of salt. But, hypothetically, Wainwright’s discovery would fundamentally change much of what we know about the origins of life on Earth and about biology in general. He says comets could seed life throughout the universe, and could, in fact, be the origin of life altogether. He says that, instead of a continuous evolution from a couple cells millions of years ago, there could be many evolutionary trees. No common ancestor, just a bunch of different common ancestors that landed here at different times.

“When I ask why they don’t believe it, they say, ‘because it can’t be true'”

Wainwright says he knows how people talk about him and he knows that few believe him. But he’s still plodding along.

“NASA is going to have to show it for people to ultimately believe it,” Wainwright said. “If NASA printed it, people would believe it. All we can do is keep putting it out, keep publishing, hope someone will look into it. It seems unbelievable.”

The thing is, maybe NASA will do it. NASA has a nascent balloon science division, and it is increasingly doing experiments in the stratosphere. And scientists have long been interested in—and have reported finding—organisms in the stratosphere. But many of those discoveries have been ignored or attributed to contaminated rockets carrying life from Earth (and back down, where it is “discovered”).

In the meantime, Wainwright is continuing to send balloons into the atmosphere. He’s hoping to run some DNA tests in the future and wants his evidence to be as rock-solid as possible.

“All we can do is keep going, we’ve got another 10 launches going out,” he said. “I give these talks at meetings and no one tells us where we’re going wrong. When I ask why they don’t believe it, they say, ‘because it can’t be true.’ There’s been a lot of complete avoidance of the issues.”

On that, Wainwright isn’t quite right. Lots of scientists have said why they’re skeptical—they’ve posited how the microbes could reach that high, they’ve said what, specifically, they need to see before they believe it’s alien life (amino acids that are unlike those found on Earth). Without seeing his paper, it’s impossible to take his newest claim any more seriously than the first one.

But still, it seems likely that Wainwright has found something up there. No scientists or journalists have suggested that he’s lying about actually finding the organisms. And that, alone, is notable. Anything that manages to survive 25 miles above the Earth’s surface is surely worth further study.