An image of Venus, made with data recorded by Japan’s Akatsuki spacecraft in 2016, shows swirling clouds in the planet’s atmosphere.
Credit: PLANET-C Project Team/JAXA

Could there be microscopic life in the clouds of the planet Venus? The idea may seem far-fetched, but in 2020, scientists discovered a tantalizing hint that it could be true, in the form of a strange gas in Venus’s atmosphere.

Venus has been called Earth’s twin. It’s next door to Earth, about the same size as Earth, and covered by an atmosphere of thick, swirling clouds. All of these features made it a tempting target during the early exploration of space. Speculators even imagined dense jungles covering the planet’s surface. When the first landers visited Venus in the 1970’s, however, they revealed a searing environment of 870 °F (465 °C) with pressures 90 times greater than that at Earth’s surface. Clouds of sulfuric acid filled the sky. The search for other life within the solar system quickly shifted to the more temperate Mars.

The new evidence was discovered by an international team of scientists that was actually more interested in exoplanets, planets orbiting distant stars. The team was led by Jane Greaves at Cardiff University in the United Kingdom. Scientists are constantly looking for ways to study exoplanets for signs of alien life. One way is to study the spectra (ranges of light) reflected by exoplanets for clues to chemicals in their atmosphere. One such chemical may be the gas phosphine. On Earth, phosphine is produced by microbes in anaerobic environments—places without oxygen. The gas is short-lived, so to be present in a planet’s atmosphere, it must be replenished continually. So, the presence of phosphine in an exoplanet’s atmosphere could be a sign of ongoing alien life.

The team recorded atmospheric data from Venus in an attempt to establish a benchmark for the spectral signature of an Earth-sized planet without phosphine. To their surprise, their findings indicated that the Venusian atmosphere did contain phosphine. After asking another team of scientists to double-check their results and studying the planet with a more powerful telescope, the evidence of phosphine was confirmed. Scientists do not yet know of a nonbiological way for phosphine to arise on Venus, pointing to the amazing possibility that Venus may harbor microscopic life. If such life exists, it is likely to be found in Venus’s clouds, where conditions are less hellish than those on the surface.

Greaves and her team emphasized that scientists are a long way from determining that there is life on Venus. The authors noted, for example, that sulfur dioxide produces a similar spectral signature to phosphine under certain conditions, raising the possibility that other molecules may mimic phosphine.

December 18, 2019

Yesterday, December 17, marked 50 years since the United States Air Force ended Project Blue Book in 1969. The project, which began in 1952, was an official research study of UFO’s (unidentified flying objects). A UFO is a light or object spotted in the air that has no obvious explanation. Some people believe UFO’s are spaceships from other planets.

Four unidentified objects appear as bright lights in the sky in this 1952 photograph taken in Salem, Massachusetts. Credit: © Popperfoto/Alamy Images

Project Blue Book began in part because of widespread public interest in UFO’s. Reports of UFO’s were increasingly occurring in the United States and around the world in the 1940′s and 1950′s. Officials in the U.S. Air Force felt obliged to investigate the phenomenon. Their reasoning was that they needed to determine where UFO’s came from and whether they posed a threat to national security. Investigators with the project collected thousands of reports and conducted many interviews with civilians and military personnel who claimed they had interactions with UFO’s in some form.

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A “flying disc” UFO was said to have crashed near Roswell, in southeastern New Mexico, in 1947. The Air Force said the mysterious craft was a weather balloon. Credit: WORLD BOOK map

Project Blue Book followed an earlier government project investigating UFO’s called Project Sign. This project began in 1947, following widespread media coverage of a UFO sighting reported by Kenneth Arnold, a civilian pilot. Arnold claimed to have seen a group of silvery, crescent-shaped craft flying at high speed near Mount Rainier, Washington, on June 24, 1947. His sighting led the press to coin the term flying saucer for UFO’s. A mysterious crash of what some people believed was a UFO near Roswell, New Mexico, was also reported that same year.

Project Sign was disbanded after one year of investigations that found little of interest. However, one member of the project, Air Force Captain Edward J. Ruppelt, argued that UFO’s were real and extraterrestrial in origin. Ruppelt is credited with coining the term UFO. Project Sign was shut down and the staff were reassigned. It was later reconstituted as Project Grudge. The investigators of this project produced a report that concluded that UFO’s were not real. However, by 1952, Ruppelt was once again asked to lead Project Blue Book, the final official government investigation of UFO’s. He was joined by the noted American astronomer J. Allen Hynek. The Project Blue Book team amassed a great number of UFO reports and sightings from many witnesses.

The U.S. Central Intelligence Agency (CIA) was tasked with evaluating the large volume of information collected during Project Blue Book. In 1953, the CIA organized a panel of scientific experts led by the physicist Howard Percy Robertson to review the material. The Robertson Panel concluded that most reported UFO sightings were worthless and declared that reasonable explanations could be suggested for most, if not all, sightings. Therefore, the panel said, the government should work to debunk (prove false) UFO sightings. However, critics argue that the panel obscured those reported UFO sightings that might have some validity.

In the years following the Robertson Panel, the directors of Project Blue Book were dismissive of most UFO reports and sightings. Publicly, the government saw UFO investigations as a waste of time. In the 1960’s, Congress established another committee to study the evidence for UFO’s. The physicist Edward Condon served as chairman of this committee. The Condon Committee issued a report in 1968 that concluded there was no genuine evidence for extraterrestrial UFO’s. The government used the report to justify ending Project Blue Book. The government took the position that UFO’s were misidentifications of known phenomena, hoaxes, or products of mass hysteria. The official records of Project Blue Book are kept at the National Archives in Washington, D.C. The records are available to the public.

May 17, 2017

Enceladus, an icy moon orbiting Saturn, is quickly becoming one of the hottest spots in the search for life beyond Earth. A group of scientists led by J. Hunter Waite of the Southwestern Research Institute in San Antonio, Texas, has determined that hydrothermal vents (flows of heated water) likely exist in a global ocean beneath Enceladus’s icy crust. These vents could possibly be home to life forms. Waite and his team published their findings last month in the journal Science.

Enceladus, a moon of Saturn, contains geysers at its south polar region that spray water vapor and grains of water ice into space. Credit: NASA/JPL/Space Science Institute

Enceladus is the sixth largest moon of Saturn. Its surface, made of bright ice, makes it the most reflective object in the solar system. Like only a few known satellites, Enceladus shows signs of ongoing geological activity. Scientists have observed a plume of particles erupting from Enceladus’s south polar region. The plume is fed by several individual jets on the surface of the moon that release mostly water vapor and grains of water ice. These jets are in turn fed by a global ocean of liquid water that exists deep beneath the moon’s surface. The jets spray material onto Enceladus’s surface and into space.

The icy surface of Enceladus, seen here in a Cassini probe image, is continually smoothed by active geysers and shows few craters. Credit: NASA/JPL/Space Science Institute

Much of what is known about the moon comes from data gathered by the Cassini spacecraft launched by the United States National Aeronautics and Space Administration (NASA) in 1997. Cassini first visited Enceladus in 2005. The ship sampled Enceladus’s geysers in 2008 and again in 2015. It detected Enceladus’s global subsurface ocean in 2015.

This artist’s conception shows Cassini nearing the rings of Saturn. Credit: NASA/JPL

Waite and his coauthors analyzed the data obtained by Cassini and found molecular hydrogen (H₂) in Enceladus’s plumes. Such hydrogen is thought to be rare in planetary bodies as small as Enceladus, which has a circumference of roughly 1,000 miles (1,600 kilometers), making it less than 1/6th the size of Earth’s moon. Waite and his team determined that the hydrogen most likely came from hydrothermal vents on a sea floor within Enceladus. On Earth, hydrothermal vents are places where heated water flows from the ocean floor. Some deep-sea vents support diverse and exotic communities of marine life. Certain microbes can use the heat of the water to produce energy. These microbes are in turn consumed or harbored by larger organisms. Scientists suspect that life could flourish around such vents on other planets or moons.

Cassini has revealed tantalizing details about Enceladus, but it will not be able to determine if life exists beneath the moon’s icy surface. Cassini’s mission is coming to an end because the craft is running out of fuel. Cassini is now making a series of orbits between Saturn and its nearest ring. In September, when Cassini completes these orbits, it will crash into Saturn. Even if Cassini could continue its mission, it would be unable to gather more detailed information on the moon’s water jets. When the probe was launched 20 years ago, astronomers had not yet observed Enceladus’s polar plumes, so they could not have included instruments to study it specifically. Energized by these new findings, engineers are now working to design a probe that can sample Enceladus’s jets in greater detail. Such a probe would carry instruments designed to look for and study organic (carbon-containing) molecules in the plumes to determine if the molecules came from living things.

October 26, 2015

The space telescope Kepler (Credit: NASA/Kepler mission/Wendy Stenzel)

We’re not saying it’s aliens…but it could be aliens. Astronomers Tabitha Boyajian and colleagues published a paper in the Monthly Notices of the Royal Astronomical Society in which they describe a star that was found to dim in a mysterious fashion over the course of their study. The star, named KIC 8462852, is 1,400 light-years from Earth. A light-year is the distance light can travel in one year, about 5.88 trillion miles (9.46 trillion kilometers).

Why is this star so puzzling to astronomers? Stars can vary in brightness slightly over time. Such objects as planets can pass in front of stars,  in an event called a transit, reducing the light visible to an observer. Astronomers can use telescopes to detect such dimming, helping them to find planets orbiting distant stars. In fact, the space telescope Kepler was observing KIC 8462852 for that very reason. But the star dimmed by as much as 20 percent, far more than what would be expected from the transit of even the largest planet. Furthermore, the dimming was not regular and periodic, as would be expected from the transit of an orbiting planet. A protoplanetary disk (a disk of dense gas circling around a young star) could cause such  significant dimming. But KIC 8462852 is a mature star, so any disk that once revolved around it should have formed planets and other orbiting bodies by now.

So, what explanations are left? Boyajian and her colleagues propose that an orbiting cloud of dust from an exocomet (a comet outside the solar system) is the most likely explanation. But others have weighed in as well. Some scientists have suggested that the star could be spinning very rapidly, causing it to become stretched and producing strange dips in brightness. Others suggested that dust and debris from a major collision between two planets could be the culprit.

A few scientists and others note that alien technology cannot yet be ruled out as a cause of the dip. They propose that an advanced alien civilization could be building huge groups of solar panels or other gigantic structures around the star. These structures would presumably be built to supply the enormous energy needs of such an advanced civilization. Such huge buildings, termed megastructures, could block out a portion of the star’s light to observers on Earth.

Now, telescopes all over the world—and in space—are trained on KIC 8462852. The next time the star dims, astronomers will be able to better track the dimming to reveal its cause. The Allen Telescope Array has focused in on the system, looking for characteristic radio transmissions that should “leak” from any advanced civilization. Soon, scientists should know more about this mysterious star. The odds that the star’s light is being blocked by alien megastructures are extremely small. But aliens or no, the unusual KIC 8462852 will help astronomers learn more about the nature of star systems.

Other World Book articles

• Astronomy
• Extraterrestrial intelligence
• SETI Institute