Sept. 16, 2008 -- More than a dozen people said they saw it -- the big bright lights in the January skies over Stephenville, Texas. It was unlike anything they'd seen before.
"I look off to the east, see some very intense bright lights coming this way at a high rate of speed," witness Steve Allen said.
The lights reconfigured into different formations several times, he said.
"Then they burst into a flame, a very unusual bright white flame," he said. "Two or three seconds of that, and then it simply disappeared."
Former military air traffic controller Paul Colcleasure said he also saw something remarkable that night.
"I honestly don't know what to think it was. I know what it wasn't," he said. "I've seen pretty much every military aircraft you can think of in the dark, and these lights were -- just the scale of the lights, the size -- not anything I can conceptualize."
In the nine months since, those lights still have not been identified.
"Ninety percent of most UFO reports are individuals who think they saw something and it's really an explainable object," said Robert Powell, in investigator with the Mutual UFO Network, an organization that investigates thousands of UFO sightings each year. "What interests MUFON the most is those cases that are unusual and there's evidence to support it."
In the Stephenville case, that evidence came in the form of radar data obtained from the Federal Aviation Administration. Powell analyzed the data and concluded that, in addition to the military jets known to be in the area, something else was in the Texas skies that night in January. Its speed and direction seemed to match the descriptions given by eyewitnesses.
"The FAA radar data that we have definitely indicates that there was an object in the sky," Powell said. "There's no doubt about that. The question becomes exactly what was the object?"
Because nearly every cell phone now comes equipped with a camera and many people have video cameras at home, most who encounter something strange in the sky have the ability to document it.
But photos and videos taken by individuals are often dismissed as fake, doctored or too blurry to be recognizable. And while more than 80 million Americans believe that we have been visited by aliens from outer space, many feel their claims are not taken seriously.
From the famous incident at Roswell, N.M., to the Phoenix Lights, UFO sightings have often been the subject of mockery. James Carrion, international director of MUFON, said he believes that because of this, many sightings go unreported.
"It's a huge problem that most folks do not want to come forward out of fear of ridicule, concern for their job, family, how they are going to be perceived in their social setting," he said.
Piquing the Interest of Scientists
UFO investigators are not the only ones fascinated with the possibility of extraterrestrial life. While mainstream scientists might not agree that aliens are visiting us on Earth, they are actively investigating the possibility that life could exist on other planets.
This summer, NASA's Phoenix Mars Lander proved conclusively that the ice on Mars is indeed frozen water, one of the key ingredients of life as we know it. Guided by NASA researchers, the robot removed a chunk of ice from Martian soil and heated it. The result was liquid water, exactly what the NASA team had hoped to find.
"We've developed a strategy for searching for life that starts with 'follow the water,'" said NASA scientist Chris McKay, who helped design the Phoenix mission. "All life on Earth needs water to grow or reproduce, so it makes sense that when we're going to other planets, we would go where we find evidence of water."
The Phoenix Lander will not be testing the soil for Martian microbes or other simple life forms -- that will be a task for future missions. But with such a promising beginning, scientists are optimistic about what they might find in the future.
"If we find that life started on Mars and on Earth, separately," McKay said, "then we know that we're not just some sort of cosmic fluke, that life is a naturally emerging phenomenon."
Peter Smith, lead scientist on the Phoenix Mars mission, agreed that the search has just begun.
"I think of Phoenix as a stepping stone, part of the long-term search for life outside the Earth," he said. "And I wish I could be a fly on the wall for the next 500 years and watch it unfold."
Leap of Faith
It's still quite a leap from believing that life exists somewhere in the universe to believing that intelligent life has visited us here on earth. But millions have already made that leap of faith. To them, the question is, when will everyone else follow?
Theoretical physicist Michio Kaku agrees that it is time for a real investigation.
"Even if there's a grain of truth, even if there's a slightest possibility that these sightings could lead to something greater, then let's look into it," Kaku said. "That's the spirit of science."