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

Venus is heating up—figuratively, that is. It has always been the hottest planet in the solar system, with surface temperatures of about 870 °F (465 °C). But new findings from the mysterious planet have been pouring in. Soon, a new generation of space probes will transform Venus from a sleepy solar system backwater to a bustling hub of scientific discovery.

Venus is the second planet from the sun. It is known as Earth’s “twin” because the two planets are so similar in size. The diameter of Venus is about 7,520 miles (12,100 kilometers). This diameter is about 400 miles (640 kilometers) smaller than that of Earth. No other planet comes nearer to Earth than does Venus. At its closest approach, it is about 23.7 million miles (38.2 million kilometers) away.

But Venus is better described as Earth’s evil twin, in respect to its withering conditions. In addition to the high temperatures, the atmospheric pressure is 90 times greater than that on Earth. Carbon dioxide makes up most of the atmosphere. The skies are strewn with clouds of sulfuric acid.

Scientists sent several probes to learn more about the planet in the 1960’s and 1970’s. But as space agencies learned of its inhospitable conditions, they concentrated their efforts elsewhere, particularly Mars. The last United States National Aeronautics and Space Administration (NASA) mission to study Venus, called Magellan, launched in 1990. Thus, scientists know relatively little about Venus, despite its close proximity to Earth and its similar size.

Despite the dearth of missions in recent years, planetary scientists continue to scan the planet with Earth-based instruments and reanalyze older data. They have returned surprising results.

Last year, a team of scientists announced that they had discovered a gas called phosphine in Venus’s atmosphere. Many living things on Earth produce phosphine; and scientists have not been able to identify any non-biological processes on Venus that might produce it. This raised the possibility that microbial life could exist in Venus’s atmosphere, where the conditions are much milder. But the discovery has been controversial. Other teams have failed to find any phosphine signature.

Last month, a team led by researchers at Queen’s University Belfast left the floating-Venusian-microbes idea high and dry. They found that Venus’s atmosphere does not contain enough water vapor to support life, irrespective of the presence of phosphine. The team determined that even the most extreme microbes on Earth require an environment with dozens of times more water than is available in Venus’s atmosphere.

Another recent study has shed light onto possible changing of Venus’s surface. Previously, Earth was the only rocky planet known to have a moving surface. A team lead by Paul Byrne, a professor at North Carolina State University, found evidence that parts of Venus’s surface might be slowly moving today. Earth’s crust slowly reshapes itself by a process called plate tectonics. Large pieces of the surface, called plates, subduct (sink) under one another, forming mountain ranges and other features. New crust forms along the ridges where the plates pull away from each other. In contrast, Byrne’s team found that pieces of Venus’s crust move like pack ice in polar oceans. Learning more about crust movement on Venus will help scientists understand how such processes develop on other planets, including Earth and exoplanets that might harbor life.

Last month, space agencies announced that not one, but three missions will be exploring Venus in the next 15 years. On June 2, NASA announced it is sending two mission to Venus. The missions were selected as part of part of NASA’s lower-cost Discovery Program. NASA expects to launch both missions between 2028 and 2030.

VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) will orbit the planet and map its surface with greater detail than ever before. It will allow scientists to better understand the planet’s features.

DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) consists of a sphere that will plunge through Venus’s thick atmosphere, studying the atmosphere’s composition. The DAVINCI+ mission planners are seeking evidence of an ocean of water that might have covered Venus’s surface eons ago.

There are other players in the new Venus boom. Last year, American company Rocket Lab announced plans to launch a small probe to Venus as early as 2023. And on June 10, just over a week after NASA’s selection DAVINCI+ and VERITAS, the European Space Agency (ESA) announced that it would also be sending a probe Venus. The EnVision orbiter will search for signs of current and former tectonic activity and the presence of a past ocean. EnVision is scheduled to arrive at Venus in 2034 or 2035.

The desire to learn more about Venus is fed by more than just curiosity about our nearest neighbor. Astronomers are looking for signs of life on exoplanets. But Venus and Earth would look quite similar from light-years away. Learning more about Venus and how it evolved to become so different from Earth will help astronomers better weed out Venus-like exoplanets in their search for ones that are more like Earth.

October 5, 2015

This map-projected view of Ceres was made from images taken by NASA’s Dawn spacecraft during its high-altitude mapping orbit in August and September of 2015.
Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Those bright spots are still a bit mysterious. Last week, the United States National Aeronautics and Space Administration (NASA) released more data from the dwarf planet Ceres (SIHR eez) taken by the probe Dawn. These data included more pictures and three-dimensional maps of Ceres’ surface.

In addition to being a dwarf planet, Ceres is the largest of the many asteroids found between the orbits of Mars and Jupiter, in a region known as the Main Belt. Ceres accounts for more than one-fourth of the total mass (amount of matter) of the Main Belt asteroids. Ceres’ shape resembles a slightly squashed sphere with a widest diameter of 605 miles (975 kilometers) and a shortest diameter of 565 miles (909 kilometers). It has a fairly smooth, rocky surface and little or no atmosphere. The dwarf planet orbits the sun every 4.6 Earth years at an average distance of about 257 million miles (414 million kilometers), and it takes its name from the Roman goddess of agriculture and the harvest.

NASA launched Dawn on September 27, 2007, just over 8 years ago. The probe studied another large asteroid in the Main Belt called Vesta before moving on to Ceres. Dawn has gone into orbit around the dwarf planet and has extensively mapped and photographed the surface. Although Ceres is pockmarked with craters like many small objects in the solar system, it does possess some interesting features. Scientists think that its rocky exterior covers a thick layer of water-ice. Though the asteroid is relatively smooth, a large, cone-shaped mountain rises four miles (six kilometers) from the surface.

And finally, there are those strange bright spots. Mostly located in the Occator (oh KAH tor) crater, these spots are far brighter than the rest of Ceres’ surface. Scientists think the spots are salt deposits, but they aren’t yet sure how they formed. In the coming months, Dawn will descend to just 230 miles (375 kilometers) above the dwarf planet. With the information gathered by this close orbit, the probe may be able to help scientists solve Ceres’ riddles.

Other World Book articles

• Exploring the Suburban Solar System (a Special report)
• Closing in on Ceres (a Behind the headline, January 21, 2015)
  

August 6, 2014

A photo of comet 67P/Churyumov-Gerasimenko taken by Rosetta on August 3, 2014, from a distance of around 180 miles (285 kilometers). (Copyright ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.)

A space probe launched in March 2004 has successfully met up with the comet it was sent to study. Ten years ago, the European Space Agency (ESA) launched the Rosetta probe, which has traveled 3.7 billion miles (6 billion kilometers) through the solar system to meet up with comet 67P/Churyumov-Gerasimenko (nicknamed Chury). The probe used a series of fly-bys past Earth and Mars to increase its speed during the chase—Chury travels at a speed of around 34,000 miles (55,000 kilometers) per hour. During the lengthy journey, the probe was put into “hibernation” for for some 2.5 years to save energy. Scientists at ESA’s flight center in Darmstadt, Germany, woke Rosetta in January for the last leg of its journey.

This morning, ESA scientists fired thrusters to stop Rosetta and maneuvered it into orbit around the comet; Rosetta will orbit Chury for the next 15 months. The probe will photograph and map the surface of the comet. Rosetta also carries a lander, Philae, which will be launched in November onto the comet’s surface. (Philae is an island in Egypt where an Egyptologist discovered an obelisk that was used in conjunction with the Rosetta Stone to decipher Egyptian hieroglyphics.) The lander carries a drill that will be used to take samples from below the surface.

Additional World Book articles:

• Comet (a research Guide)
• Space exploration

July 30, 2014

Geysers in the solar polar region of Saturn’s moon Enceladus are actually fountains erupting from an underground ocean of liquid water, according to a new study by scientists working with the Cassini space probe. The discovery solves a 10-year puzzle about the source of the geysers, which shoot water vapor and tiny particles of ice hundreds of kilometers into space. Discovered by Cassini in 2005, the geysers erupt from four “tiger-stripe” fractures, each of which is some 80 miles (130 kilometers) long and 1 1/2 miles (2.4 kilometers) wide. Cassini scientists confirmed the existence of the ocean in 2013.

Plumes of ice particles and water vapor erupt from Enceladus in a false-color image taken by Cassini. Some of the particles become part of one of Saturn's rings. (NASA/JPL/Space Science Institute)

Heat-detection equipment on Cassini had found that the fractures were warmer than the surrounding terrain. Some scientists had theorized that heat created as the sides of the fractures rubbed against one another under Saturn’s gravitational pull was producing the geysers. The new study has revealed that the geysers are actually producing the surface heat by transporting water vapor and water droplets from deep inside the moon. As the water vapor condenses near the surface, it also releases heat. The excess heat causes the water to erupt in geysers. Buried beneath about 20 miles (32 kilometers) of surface ice, the sea is centered on the moon’s south pole, though it may extend much farther around the moon.

The "tiger-stripe" fractures from which the geysers erupt score a basin surrounding Enceladus's south pole. (NASA/JPL-Caltech/SSI)

Geysers appear as colored bars in a three-dimensional model of Enceladus's south polar region. (ASA/JPL-Caltech/Space Science Institute)

Additional World Book articles:

• Cassini, Giovanni Domenico
• Satellite
• Space exploration
• Close Encounters with Saturn (a Special Report)
• Probing the Planets (a Special Report)

May 1, 2013

Scientists have discovered a hurricane on Saturn that is 20 times as large as the average hurricane on Earth. NASA’s Cassini spacecraft has provided scientists with the first close-up views of the enormous storm swirling around Saturn’s north pole. The hurricane swirls inside a mysterious six-sided feature first photographed in 2006. The hexagon is unlike anything seen on any other planet. The Cassini probe was able to photograph the storm in sunlight only after the planet’s north pole emerged from the darkness of its polar winter. Cassini’s orbit was also shifted so the probe would pass directly over the north pole.

The eye of the hurricane is about 1,250 miles (2,000 kilometers) wide. The clouds circling around the outer edge of the storm are moving at 330 miles  (530 meters) per hour. By contrast, the strongest hurricanes on Earth have winds of up to 200 miles (320 kilometers) per hour. Also, unlike hurricanes on Earth, which generally move, the Saturnian hurricane is locked onto the planet’s north pole. Scientists believe it has been churning for years.

A hurricane swirls around the north pole of Saturn, in a false-color infrared image taken by the Cassini space probe at a distance of about 261,000 miles (419,000 kilometers). Clouds shown in red are closer to the surface than those shown in green. (NASA/JPL-Caltech/SSI)

“We did a double take when we saw this vortex because it looks so much like a hurricane on Earth,” noted Cassini imaging team member Andrew Ingersoll. “But there it is at Saturn, on a much larger scale, and it is somehow getting by on the small amounts of water vapor in Saturn’s hydrogen atmosphere.”

Hurricanes on Earth feed off warm ocean water. But there is no body of water close to these clouds high in Saturn’s atmosphere. Scientists suggest learning how these Saturnian storms use water vapor could provide greater understanding of how hurricanes on Earth are generated and sustained.

Additional World Book articles

• Jet Propulsion Laboratory
• Close encounters with Saturn (a special report)
• Probing the Planets (a special report)
• Space exploration 1997 (a Back in Time article)
• Space exploration 2004 (a Back in Time article)
• Space exploration 2008 (a Back in Time article)

July 12, 2012

Astronomers using the Hubble Space Telescope (HST) have discovered another moon orbiting Pluto, announces NASA. The new satellite is the fifth found circling the small body, which for decades was widely considered the ninth planet in the solar system. Pluto was “demoted” from planet to a new category of space object called “dwarf planet” after astronomers in the 1990′s found many objects similar to Pluto in the outer reaches of the solar system, in an area called the Kuiper Belt. Pluto was discovered by Clyde W. Tombaugh in 1930, based on predictions by astronomer Percival Lowell in 1905. Pluto is 1,460 miles (2,350 kilometers) in diameter.

Pluto is so far from Earth and is so small that even powerful telescopes reveal little detail of its surface. The Hubble Space Telescope gathered the light for the pictures of Pluto shown here. (NASA)

Astronomers with the SETI Institute, a research organization that searches for life in the universe beyond Earth, discovered the new moon and gave it the temporary name P5. The astronomers are using the HST to study Pluto in preparation for a fly-by of the dwarf planet by the New Horizons space probe in July 2015. New Horizons was launched in 2006 to explore Pluto, its largest moon Charon, and other objects in the Kuiper Belt.

According to the researchers, P5 is a tiny, irregularly shaped body that measures from 6 to 15 miles (10 to 25 kilometers) across. The astronomers were unable to get a closer measurement because Pluto and its moons are about 2.8 billion miles (4.7 billion kilometers) away from Earth. Pluto’s moon Charon, which is about 750 miles (1,207 kilometers) in diameter, was discovered in 1978. Hydra and Nix, each up to 100 miles (160 kilometers) in diameter, were found in 2005. Pluto’s fourth moon, P4, discovered in 2011, is about 8 to 21 miles (13 to 34 kilometers) in diameter.

The scientists were a bit disconcerted by the discovery of an unknown moon as New Horizons is nearing Pluto. “All of this stuff poses a navigation hazard for New Horizons,” according to Ray Villard, news director of the Space Telescope Science Institute. However, tiny P5 has also produced a sense of wonder at the complexity of ex-planet Pluto’s system of satellites.

Additional World Book articles:

• Space exploration
• Exploring the Suburban Solar System (a special report)
• Astronomy 1930 (Back in Time article)
• Astronomy 1978 (Back in Time article)
• Astronomy 2006 (Back in Time article)
• Space exploration 2006 (Back in Time article)

March 27, 2012

Sometimes things are not as simple as they appear. Take the planet Mercury, for instance. In a very short time, the smallest planet in the solar system (sorry Pluto, you’re no longer a planet) has gone from a simple hunk of rock, much like Earth’s moon, to one of the most unusual planets ever studied. For years, most astronomers thought that Mercury formed early in the solar system’s history and has since remained pretty much unchanged. New evidence shows a planet whose more recent history includes active volcanoes, a shifting crust, and other activities once thought to have ended billions of years ago. Some of these activities may result from the fact that Mercury is slowly shrinking. The shrinking would explain why the outer layer of the planet is buckling and cracking. A closer look at the surface also shows evidence of lava flows having occurred much more recently than previously thought.

The MESSENGER space probe has revealed surprising new findings about the smallest planet in the solar system. (Courtesy of NASA)

The planet’s surface is not the only surprise. Mercury may also have an internal structure like no other planet yet studied by scientists. Mercury appears to have a core consisting of three layers. Earth has only two such inner layers. Both Mercury and Earth have an inner core of solid metal surrounded by a second layer of liquid metal. Unlike Earth, Mercury appears to have a third layer made of solid iron and sulfur. Many scientists now speculate that this possible third layer of core explains one of the great mysteries concerning Mercury. Scientists have long wondered how the planet could be so small and yet have a much greater mass than the other inner planets–Venus, Earth, and Mars–for its size.

The new data on Mercury was collected by the MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) space probe. Launched in 2004 by NASA, MESSENGER began a one-year mission orbiting Mercury in early 2011 (which NASA scientists have now extended). The probe reached the planet after a more than five-year tour of the inner solar system. The long, looping route involved three close fly-bys of Mercury along with close approaches to Venus and Earth.

Just how loopy was the route MESSENGER took? Mercury is only about 20 percent farther from Earth than Mars when those planets pass closest to Earth. Yet, a probe going to Mars travels for less than a year. By comparison, MESSENGER took more than five years to reach Mercury.

Additional World Book articles

• Probing the Planets (a special report)
• Space Exploration 2004 (Back in Time article)
• Space Exploration 2008 (Back in Time article)
• Space Exploration 2009 (Back in Time article)
• Space Exploration 2011 (Back in Time article)

Jan. 3, 2012

Did Earth once have two moons? Does the moon have an iron core? Where should astronauts or unpiloted probes land for future missions to the moon? Information gathered by two new NASA probes orbiting Earth’s single natural satellite may soon help scientists answer these questions and several more. Launched on Sept. 10, 2011, the twin spacecraft of the GRAIL mission (Gravity Recovery and Interior Laboratory) went into orbit around the moon on December 31, and Jan. 1, 2012. Their mission is to create the most detailed map of the moon’s gravitational field ever made.

GRAIL-A and GRAIL-B were to spend the next two months gradually orbiting closer and closer to the surface until they are flying in formation at an altitude of only about 34 miles (55 kilometers). Then in March, instruments on-board the probes will start measuring the distance between them to within a few microns–the width of a human blood cell. That distance will vary as differences in the gravitation field caused by mountains, craters, and other surface features as well as features belowground cause the probes to speed up or slow down slightly. The probes will then radio this information to scientists at the Jet Propulsion Laboratory in Pasadena, California.

A tremendous collision between Earth and a smaller object led to the birth of the moon. Debris from the impact went into orbit in a ring around Earth, then gathered together to form the moon.        © William K. Hartmann

The second-moon theory is one explanation for the startling differences between the smoother near side and higher, more-mountainous far side of the moon. Scientists believe that the moon formed as a result of a collision 4.6 billion years ago between Earth and an object roughly the size of the planet Mars. Vaporized rock from Earth’s surface blasted into orbit around Earth then gradually cooled into solid bodies that gathered together. Some scientists believe that a second, much-smaller moon formed at the same time. They have theorized that after 10 million to 100 million years, the smaller moon collided with its larger companion. During the impact, the smaller moon flattened itself against the far side of the moon, creating the elevated highlands there. The gravitational map should show evidence of this impact, if it occurred, along with the answers to many other questions.

Additional World Book articles

• Armstrong, Neil
• Galileo (Mature scientific career)
• How the Moon Was Born (A Special Report)
• Space exploration (Lunar probes)