After 10 months of investigation, the Pentagon still doesn’t know if extraterrestrials are flying overhead.

In a long-awaited report released last week investigating 144 unidentified aerial phenomena, or UAPs, spotted between 2004 and 2021, they were able to explain only a single event: likely a balloon.

These sightings were reported by military pilots detecting inexplicable anomalies with aircraft cameras, which showed distant orbs hovering and appearing to dart through the sky.

Yet even with military-grade sensors, the report shows no evidence of extraterrestrials, even if some of the objects appeared to move with unusual speed and agility. Instead, the task force came up with alternate explanations, including airborne clutter, natural atmospheric phenomena, and military or industrial technology. Separately, the report acknowledges that “some UAP may be attributable to sensor anomalies.”

But scientists who specialize in studying the skies think there are more answers to be found.

“Just because we haven’t necessarily converged on what the explanation is, the base assumption is that it’s probably something we can explain if we have enough data,” said Melanie Good, a lecturer in physics and astronomy at the University of Pittsburgh.

Mark Miller, a professor of atmospheric science at Rutgers University, isn’t surprised that preliminary results are inconclusive. He has spent his career pointing cameras at the skies to study complex patterns of clouds and energy in the atmosphere, so he knows just how hard it can be.

“We’re always seeing new things and it always takes a while to reconcile what we’re seeing when we deploy these more advanced sensors,” he said. “In a sense, we expect the unexpected.”

Moreover, these particular sensors might not be up to the task of finding UAPs.

“Military equipment is not designed to provide the best scientific data,” said Avi Loeb, a professor of science at Harvard University who studies astrophysics. “It’s designed to do something useful for the military” — to quickly detect and report a potential threat.

Miller added that the kind of equipment required to collect high quality data on UAPs would be more than what a small fighter jet needs or could accommodate.

A variety of high-tech sensors from military aircraft collected the UAP data used in the investigation, but each sensor still has its quirks. Infrared, for example, detects heat energy. Planes use forward-looking infrared (FLIR) to see through fog or smoke that obscures their vision. A FLIR camera on a naval plane recorded a video of a heat-emitting orb in 2004, and another video was captured in 2015.

Radar, on the other hand, works by sending out radio waves and measuring how much is reflected back. In planes, its purpose is to detect the position and speed of hazards in the surrounding airspace; radar is what alerted the pilots in 2004 to investigate the UAP.

Astrophysicists, meteorologists, and atmospheric scientists use similar sensors for their own research and are well-versed in all the ways they can go wrong. Miller says there’s especially high risk of false readings with new sensor technology, which has proven true for past UFO sightings.

“I can’t tell you the number of occasions in the past when we’ve deployed a new sensor, and then discovered artifacts over time,” Miller said. In particular, these unexpected blips can arise from the complex calculations that computers have to do to create an image — but to unravel that, scientists would need the raw data from the sensors, not just the final image, he said.

Optical illusions can also occur because of the sensor’s position, Good said. One example, the bokeh effect, occurs when the opening in the camera reshapes out-of-focus light, Good said. Objects can also appear to have unusual velocity if the viewer misjudges their distance.

And the biggest variable of all: the sky. Even if it seems like a void, the sky is actually chock full of water droplets and ice crystals forming clouds, birds and bugs, balloons, and other debris, not to mention the energy and heat fluctuations that create phenomena like the Northern Lights, said Drew Anderson, a meteorologist at WFMZ-TV 69 News and adjunct professor at West Chester University.

The report acknowledges this, specifying that natural atmospheric phenomena such as ice crystals, moisture, or heat could account for part of the UAP sightings. Sensors depend on waves traveling through the air to signal that an object exists. But when these waves encounter other particles in the air, like ice crystals, water droplets — or even pollen and pollution — the particles can disrupt the wave’s path back to the sensor in both predictable and unpredictable ways. Pockets of heat or other energy building up in the atmosphere may also show up on IR.

That’s why it can be hard to detect objects accurately in unfamiliar places, Miller said. He pointed to one UAP sighting in California in July, a time when the clouds around California are particularly low and can appear denser based on pollution.

“You’re at the mercy of the atmosphere,” Miller said.

However, the fact that more than half the sightings were detected on multiple sensors that use different detection methods may signal that it’s not an error, Loeb said.

More than half of Americans surveyed by Pew Research Center think military reports of UAPs are probably evidence of life on other planets, and 87% don’t see UAPs as a major threat.

So, what would it take to study UAPs in earnest? For starters, collaborative science and funding, Loeb said.

They’d also need the right technology. Wide-field cameras — like the one on the Hubble Space Telescope — could help scientists look for UAPs in larger sections of the sky. A network of multiple high-end research sensors would need to be optimized to measure the right kinds of heat, movement, and size. They would also need more powerful computers for storing, processing, and sharing the data.

UAP research “should move to the realm of science where we will collect more evidence in an open fashion,” Loeb said. “The sky is not classified.”