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.

January 8, 2020

Late last year, on Dec. 18, 2019, the European Space Agency (ESA) launched the CHEOPS telescope into space, where it will study the composition of exoplanets. Exoplanets, or extrasolar planets, orbit stars other than our sun. The CHEOPS telescope was launched aboard a Russian-made Soyuz rocket from the Guiana Space Center on the northern coast of South America. CHEOPS—pronounced KAY ops—is an acronym for Characterizing Exoplanets Satellite. If the acronym sounds familiar, Cheops was also the Greek name of the ancient Egyptian king Khufu, who constructed the Great Pyramid at Giza.

A Soyuz rocket carrying the ESA’s CHEOPS telescope lifts off from the Guiana Space Center on Dec.18, 2019. Credit: ESA/S. Corvaja

CHEOPS is small for a satellite, measuring just 5 feet (1.5 meters) long. The craft turns within a polar orbit that allows it to fly between night and day. Its back, covered in solar panels, receives continuous sunshine, while the telescope and camera on the other side is always peering into dark, sunless, and limitless space.

This artist’s impression shows CHEOPS with its back to the sun and the telescope pointed into dark space. Credit: ESA/C. Carreau

The CHEOPS mission is not to discover new exoplanets, but rather to learn more about the exoplanets we already know exist. CHEOPS will study exoplanets larger than our own Earth but smaller than the planet Neptune. Scientists want to know if these intermediate sized exoplanets are more like “super-Earths”—large rocky worlds—or “mini-Neptunes”—small gas giants. By studying an exoplanet’s atmosphere, diameter, mass, and other properties, CHEOPS can determine its composition and whether or not it might be able to support life. Astronomers have discovered over 4,000 exoplanets so far, but there are likely hundreds of billions more to be found.

CHEOPS will use the transit method to study exoplanets. It will aim its camera at a star and capture periodic dips in the star’s light output. These dips occur when an exoplanet passes in front of—or transits—a star in relation to CHEOPS’s point of view.

CHEOPS is a stepping stone between the first exoplanet observatories, such as Kepler and COROT, and the powerful observatories of the near future. The United States National Aeronautics and Space Administration (NASA) James Webb Space Telescope (JWST), scheduled for launch in 2021, will be able to determine the gases present in the atmospheres of some exoplanets and even record low detail images of those gases. The European Southern Observatory’s Extremely Large Telescope (ELT) will also be able to image rocky exoplanets and characterize their atmospheres after it is completed in 2025. The ELT is a ground-based observatory being built in the Atacama Desert of northern Chile. Kepler and COROT prepared the way for CHEOPS, and the JWST and ELT will further examine the most promising CHEOPS targets as scientists continue the hunt for extraterrestrial life.

April 24, 2018

Last week, on April 18, a next-generation planet-hunting satellite was carried into orbit. The Transiting Exoplanet Survey Satellite (TESS) was launched from Cape Canaveral in Florida. Designed by the United States National Aeronautics and Space Administration (NASA), TESS will search for exoplanets (planets orbiting stars beyond our solar system).

At Cape Canaveral Air Force Station in Florida, the SpaceX Falcon 9 rocket carrying NASA’s Transiting Exoplanet Survey Satellite (TESS) lifts off on April 18, 2018. Credit: SpaceX

TESS was carried into space by a SpaceX Falcon 9 rocket. After boosting the satellite into orbit, the first stage of the rocket landed on a crewless barge in the Atlantic Ocean and will be used again. When TESS reaches its desired orbit, it will undergo testing and calibration before it begins the search for exoplanets.

TESS will replace NASA’s planet-hunting satellite Kepler, which is almost out of fuel. Launched in 2009, Kepler has discovered thousands of exoplanets. Like Kepler, TESS will use the transit method to search for exoplanets. As an exoplanet passes in front of its parent star, it blocks out a tiny portion of the star’s light (an event called a transit). TESS can detect these telltale dips in the intensity of the light.

NASA’s Transiting Exoplanet Survey Satellite (TESS), shown here in a conceptual illustration, will identify exoplanets orbiting stars beyond our solar system. Credit: NASA Goddard Space Flight Center

Although TESS will use the transit method, it is far from a Kepler clone. TESS will study brighter stars than Kepler did. This means that all of TESS’s targets will be at most 200 light-years from Earth. Because TESS is limited to closer, brighter stars, it will be easier for astronomers to confirm the finds and perform follow-up studies. TESS will also be able to observe the whole sky, as opposed to Kepler’s ability to only study small sections of sky at a time. TESS will also focus its search on finding Earth-sized exoplanets, especially those that orbit their star in the habitable zone, the range of an orbit where liquid water may be present on a planet’s surface. Liquid water is necessary for all life on Earth.

One of the tools astronomers will use to follow up on TESS’s discoveries will be NASA’s James Webb Space Telescope (JWST). The JWST is the most powerful space telescope ever built. Due to launch in 2020, it will be able to search for possible signs of life on the planets that TESS finds. Another observatory will be the Characterizing Exoplanets Satellite (CHEOPS). Designed by the European Space Agency, CHEOPS will launch at the end of 2018. Rather than being strictly a planet hunter, CHEOPS will focus on studying the makeup of smaller exoplanets that have already been discovered. It will likely be able to better define some of the exoplanets TESS discovers.

Astronomers have long hoped to learn whether—and, if so, where—other life exists in the universe. With TESS, JWST, and CHEOPS, they will be able to pinpoint nearby exoplanets with potential for life. But it will likely take even more advanced telescopes to determine if the planets actually teem with living things, like Earth.