A US task force is examining 800 unidentified anomalous phenomena, but less than 5 per cent of them are thought to be "really abnormal".
NASA held its first public meeting on UFOs on Wednesday, a year after launching a study to unravel the unexplained sightings that have long fascinated the general public.
The space agency televised the four-hour hearing featuring an independent panel of experts who vowed to be transparent. The team was made up of 16 scientists and other experts selected by NASA, including retired astronaut Scott Kelly, the first American to spend nearly a year in space.
The studies seek to probe what NASA calls UAP- short for unexplained anomalous phenomena - in the sky, in space or under the sea.
The subject is a very serious one, the US space agency stressed, as it concerns both national security and air traffic safety.
Still, hundreds of questions from the public that poured in ahead of time were skeptical and veered into conspiracy theories.
“I want to emphasise this loud and proud: There is absolutely no convincing evidence for extraterrestrial life associated with” unidentified objects, NASA's Dan Evans said after the meeting.
Optical illusions can explain some of these, said Kelly. He recalled an episode years ago at Virginia Beach - on the east coast of the United States - during which his radar intercept officer in the back seat was convinced they’d flown past a UFO.
“It turns out it was Bart Simpson, a balloon,” he said. “And in my experience, the sensors kind of have the same issues as the people’s eyeballs”.
Some 800 unidentified aerial phenomena have been collected, Sean Kirkpatrick, director of the All-domain Anomaly Resolution Office, said on Wednesday. But "maybe only between 2 per cent and 5 per cent" are "really abnormal,” he said.
During the meeting - held at NASA’s headquarters in Washington with the public taking part remotely - Kirkpatrick showed two videos. The first depicted a spherical object seen in the Middle East in 2022, and still unexplained today.
A second video showed three dots that appeared to be moving back and forth in a mysterious way. He explained these were actually aircraft in an air corridor, whose back-and-forth movements were caused by oscillations in the sensor itself.
Online harassment from sceptics
Since last June, some of the group's experts have been subject to online harassment from sceptics.
Throughout the meeting, live-streamed on NASA’s YouTube feed - many viewers wrote comments accusing panel members of lying or covering up evidence of extraterrestrial life.
These acts reinforce the stigma surrounding the topic, said NASA's chief, who added that the agency's security is dealing with the issue.
"It is really disheartening to hear of the harassment that our panellists have faced online because they're studying this topic," Nasa science chief Nicola Fox said during the meeting. "Harassment only leads to further stigmatisation".
“It’s precisely this rigorous, evidence-based approach that allows one to separate the fact from fiction," said Evans.
In an effort to overcome the negative connotations, the official designation UFO has been substituted with the more neutral and descriptive "unidentified abnormal phenomenon" (UAP).
What does the panel hope to find?
Perhaps new physical phenomena, argued some experts.
“If NASA applies the same methodological rigour to the study of anomalous unidentified phenomena as to that of possible extraterrestrial life, then we will be in a position to learn something new and interesting, whatever the final explanation,” said David Grinspoon, one of the scientists on the panel.
Mike Gold, a former NASA official also on the panel, advocated the creation of a dedicated office within the space agency.
NASA’s final report, expected by the end of July, will make recommendations to the government, and it will probably include ways of better integrating public observations.
“Collecting more good data from the scientific community to review in a peer-reviewed context will be important for progress to be made here,” said Nadia Drake, a panel member and science journalist.
In science, scepticism is not a bias, nor is it a bad word, she added. Discussing how the space organisation could tackle the topic of UAPs scientifically, she said: “I think its important to remember that it is not NASA's job to replicate the efforts of the Department of Defense but rather to consider approaches that are complementary”.