There’s a planet next door that could explain the origins of life in the universe. It was probably once covered in oceans. It may have been able to support life for billions of years. No surprise, astronomers are desperate to land spacecraft there.
The planet is not Mars. It’s Earth’s twin, Venus.
Despite its appeal, the second planet from the sun is one of the hardest places in the solar system to get to know. That’s partly because modern Venus is famously hellish. Temperatures are hot enough to melt lead. Choking clouds of sulfuric acid swirl through its atmosphere.
Today, researchers who want to explore Venus say they have the technology to master such challenging conditions. “There’s a perception that Venus is a very difficult place to have a mission,” says Darby Dyar. She is a planetary scientist at Mount Holyoke College in South Hadley, Mass. “Everybody knows about the high pressures and temperatures on Venus, so people think we don’t have technology to survive that. The answer is that we do.”
Indeed, researchers are actively developing Venus-defying technology.
In 2017, there were five proposed Venus projects. One was a mapping orbiter. It would probe the atmosphere as it fell through it. Others were landers that would zap rocks with lasers. From a technology point of view, all were considered ready to go. And the laser team actually got money to develop some parts for the system. But the other programs failed to find funding.
“Earth’s so-called ‘twin’ planet Venus is a fascinating body,” notes Thomas Zurbuchen. He is the associate administrator for NASA’s science mission programs in Washington, D.C. The problem, he explains, is that “NASA’s mission selection process is highly competitive. By that he means that right now there are more good ideas than money available to build them all.
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In the search for alien life, Venus and Earth would look equally promising from afar. Both are roughly the same size and mass. Venus lies just outside the sun’s habitable zone. That zone has temperatures that could keep liquid water stable on a planet’s surface.
No spacecraft have landed on the surface of Venus since 1985. A few orbiters have visited Earth’s neighbor in the past decade. The European Space Agency’s Venus Express was one. It visited Venus from 2006 to 2014. The other is the Japanese space agency’s Akatsuki. It has been orbiting Venus since December 2015. Still, no NASA craft has visited Earth’s twin since 1994. That's when the Magellan craft plunged into the atmosphere of Venus and burned up.
One obvious barrier is the planet's thick atmosphere. It is 96.5 percent carbon dioxide. That blocks scientists’ view of the surface in almost all wavelengths of light. But it turns out that the atmosphere is transparent to at least five wavelengths of light. That transparency could help identify different minerals. And Venus Express proved it would work.
Looking at the planet in one infrared (In-frah-RED) wavelength allowed astronomers to see hot spots. These might be signs of active volcanoes. An orbiter that used the other four wavelengths might learn even more, Dyar says.
To really understand the surface, scientists want to land a craft there. It would have to contend with the opaque atmosphere while looking for a safe place to touch down. The best map of the planet’s surface is based on radar data from Magellan a quarter century ago. Its resolution is too low to show rocks or slopes that might topple a lander, notes James Garvin. He works at NASA’s Goddard Space Flight Center in Greenbelt, Md.
Garvin is part of a team that’s testing a computer-vision technique. Called Structure from Motion, it could help a lander map its own touch-down site. It would do this during its descent. The system quickly analyzes many images of stationary objects taken from different angles. This allows it to create a 3-D rendering of the surface.
Garvin's group tried it out with a helicopter over a quarry in Maryland. It was able to plot boulders less than half a meter (19.5 inches) across. That’s about the size of a basketball hoop. He is scheduled to describe the experiment in May at the Lunar and Planetary Science Conference in The Woodlands, Texas.
Any lander that survives to reach the surface of Venus faces another challenge: surviving.
The first landers there were Soviet spacecraft. They landed in the 1970s and 1980s. Each lasted only an hour or two. That's not surprising. The planet’s surface is about 460° Celsius (860° Fahrenheit). The pressure is some 90 times that of Earth’s at sea level. So in short order some crucial component will melt, become crushed or corrode in the acidic atmosphere.
Modern missions are not expected to fare much better. It could be one hour — or maybe 24 hours “in your wildest dreams,” Dyar says.
But a team at NASA’s Glenn Research Center in Cleveland, Ohio is hoping to do far better. It aims to design a lander that would last months. “We’re going to try to live on the surface of Venus,” explains Tibor Kremic. He is an engineer at the Glenn center.
Past landers have used their bulk to temporarily absorb heat. Or they have countered scorching temps with refrigeration. Kremic’s team proposes something new. They plan to use simple electronics. Made of silicon carbide, these should withstand the heat and do a reasonable amount of work, says Gary Hunter. He is a NASA Glenn electronics engineer.
His group has tested the circuits in a Venus simulation chamber. Called GEER, it’s short for Glenn Extreme Environment Rig. Kremic compares it to “a giant soup can.” This one has walls 6 centimeters (2.4 inches) thick. The new type of circuits still worked after 21.7 days in an atmosphere that simulated Venus.
The circuits could have lasted longer, Hunter suspects, but didn't get a chance. Scheduling issues put an end to the test.
The team now hopes to build a prototype lander that would last for 60 days. On Venus, that would be long enough to act as a weather station. “That has never been done before,” Kremic notes.
And that presents the next challenge. Planetary scientists have to figure out how to interpret such data.
Rocks interact with the Venusian atmosphere differently than they would with the surface atmosphere on Earth or Mars. Mineral specialists identify rocks based on the light they reflect and emit. But the light that a rock reflects or emits can change in high temperatures and pressures. So even when scientists get data from the rocks on Venus, understanding what they show could prove tricky.
Why? “We don’t even know what to look for,” Dyar admits.
Ongoing experiments at GEER will help here. Scientists can leave rocks and other materials in the chamber for months, then see what happens to them. Dyar and her colleagues are doing similar experiments in a high-temperature chamber at the Institute of Planetary Research in Berlin.
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“We try to understand the physics of how things happen on the Venus surface so we can be better prepared when we explore,” Kremic says.
There are other ways to explore rocks, too. Two approaches NASA didn’t yet fund would use different techniques. One would maintain Earthlike conditions inside, then bring crushed rocks into a chamber for study. Another shoots rocks with a laser, then analyzes the resulting puff of dust. The Mars Curiosity rover uses this technique.
But their high costs are putting some planned tests on indefinite hold. Last year, NASA issued a research challenge. It is looking for candidate missions to Venus that could get there for $200 million or less.
“The Venus community is torn on this idea,” Dyar says. It would be hard to make meaningful headway on science questions at such a low cost, she notes. Still, she concedes, it may take multiple piecemeal missions to understand Venus anyway. “We’ll get the frosting on one trip and the cake on a different trip.”
Lori Glaze works on a Venus project at NASA Goddard. “My new favorite saying for the Venus community,” she says, is "Never give up, never surrender." So, she notes, “We keep trying.”
acidic An adjective for materials that contain acid. These materials often are capable of eating away at some minerals such as carbonate (or preventing their formation in the first place).
alien (in astronomy) Life on or from a distant world.
angle The space (usually measured in degrees) between two intersecting lines or surfaces at or close to the point where they meet.
astrobiologist The study of life everywhere in the universe, including on Earth and in space. A scientist who works in this field is known as an astrobiologist.
astronomy The area of science that deals with celestial objects, space and the physical universe. People who work in this field are called astronomers.
atmosphere The envelope of gases surrounding Earth or another planet.
carbon dioxide (or CO2) A colorless, odorless gas produced by all animals when the oxygen they inhale reacts with the carbon-rich foods that they’ve eaten. Carbon dioxide also is released when organic matter burns (including fossil fuels like oil or gas). Carbon dioxide acts as a greenhouse gas, trapping heat in Earth’s atmosphere. Plants convert carbon dioxide into oxygen during photosynthesis, the process they use to make their own food.
chemical A substance formed from two or more atoms that unite (bond) in a fixed proportion and structure. For example, water is a chemical made when two hydrogen atoms bond to one oxygen atom. Its chemical formula is H2O. Chemical also can be an adjective to describe properties of materials that are the result of various reactions between different compounds.
circuit A network that transmits electrical signals. In the body, nerve cells create circuits that relay electrical signals to the brain. In electronics, wires typically route those signals to activate some mechanical, computational or other function.
colleague Someone who works with another; a co-worker or team member.
component Something that is part of something else (such as pieces that go on an electronic circuit board or ingredients that go into a cookie recipe).
density The measure of how condensed some object is, found by dividing its mass by its volume.
electronics Devices that are powered by electricity but whose properties are controlled by the semiconductors or other circuitry that channel or gate the movement of electric charges.
engineer A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.
environment The sum of all of the things that exist around some organism or the process and the condition those things create. Environment may refer to the weather and ecosystem in which some animal lives, or, perhaps, the temperature and humidity (or even the placement of components in some electronics system or product).
habitable A place suitable for humans or other living things to comfortably dwell.
lander A special, small vehicle designed to ferry humans or scientific equipment between a spacecraft and the celestial body they will explore.
laser A device that generates an intense beam of coherent light of a single color. Lasers are used in drilling and cutting, alignment and guidance, in data storage and in surgery.
lunar Of or relating to Earth’s moon.
Mars The fourth planet from the sun, just one planet out from Earth. Like Earth, it has seasons and moisture. But its diameter is only about half as big as Earth’s.
mass A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.
mineral Crystal-forming substances that make up rock, such as quartz, apatite or various carbonates. Most rocks contain several different minerals mish-mashed together. A mineral usually is solid and stable at room temperatures and has a specific formula, or recipe (with atoms occurring in certain proportions) and a specific crystalline structure (meaning that its atoms are organized in regular three-dimensional patterns).
NASA Short for the National Aeronautics and Space Administration. Created in 1958, this U.S. agency has become a leader in space research and in stimulating public interest in space exploration. It was through NASA that the United States sent people into orbit and ultimately to the moon. It also has sent research craft to study planets and other celestial objects in our solar system.
opaque Unable to see through, blocking light.
orbiter A spacecraft designed to go into orbit, especially one not intended to land.
perception The state of being aware of something — or the process of becoming aware of something — through use of the senses.
physics The scientific study of the nature and properties of matter and energy. Classical physics is an explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion.
planet A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and has cleared other objects out of the way in its orbital neighborhood.
planetary science The science of planets other than Earth.
pressure Force applied uniformly over a surface, measured as force per unit of area.
prototype A first or early model of some device, system or product that still needs to be perfected.
radar A system for calculating the position, distance or other important characteristic of a distant object. It works by sending out periodic radio waves that bounce off of the object and then measuring how long it takes that bounced signal to return. Radar can detect moving objects, like airplanes. It also can be used to map the shape of land — even land covered by ice.
silicon A nonmetal, semiconducting element used in making electronic circuits. Pure silicon exists in a shiny, dark-gray crystalline form and as a shapeless powder.
simulate (in computing) To try and imitate the conditions, functions or appearance of something. Computer programs that do this are referred to as simulations.
solar system The eight major planets and their moons in orbit around our sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.
sulfuric acid A strong acid having the chemical formula H 2 SO 4 . Used as a drain cleaner and in lead-acid car batteries, the liquid is able to burn tissues and eat through metals and even rock.
sun The star at the center of Earth’s solar system. It’s an average size star about 26,000 light-years from the center of the Milky Way galaxy. Also a term for any sunlike star.
technology The application of scientific knowledge for practical purposes, especially in industry — or the devices, processes and systems that result from those efforts.
universe The entire cosmos: All things that exist throughout space and time. It has been expanding since its formation during an event known as the Big Bang, some 13.8 billion years ago (give or take a few hundred million years).
Venus The second planet out from the sun, it has a rocky core, just as Earth does. Venus lost most of its water long ago. The sun’s ultraviolet radiation broke apart those water molecules, allowing their hydrogen atoms to escape into space. Volcanoes on the planet’s surface spewed high levels of carbon dioxide, which built up in the planet’s atmosphere. Today the air pressure at the planet’s surface is 100 times greater than on Earth, and the atmosphere now keeps the surface of Venus a brutal 460° Celsius (860° Fahrenheit).
wavelength The distance between one peak and the next in a series of waves, or the distance between one trough and the next. Visible light — which, like all electromagnetic radiation, travels in waves — includes wavelengths between about 380 nanometers (violet) and about 740 nanometers (red). Radiation with wavelengths shorter than visible light includes gamma rays, X-rays and ultraviolet light. Longer-wavelength radiation includes infrared light, microwaves and radio waves.
Meeting: D. Dyar. Venus: Our misunderstood sister. American Astronomical Society Meeting, Oxon Hill, Md., January 11, 2018.
Meeting: T. Kremic, G. Hunter and J. Rock. LLISSE: A long duration Venus surface probe. 15th meeting of the Venus Exploration Analysis Group, Laurel, Md., November 14, 2017.
Journal: P. Neudeck et al. Prolonged silicon carbide integrated circuit operation in Venus surface atmospheric conditions. AIP Advances. Vol. 6, December 2016. doi: 10.1063/1.4973429.