Putting a lander on Earth’s ‘evil twin’

U. COLORADO (US)—What would it take to land a spacecraft on Venus? NASA has asked a research team at the University of Colorado at Boulder to help answer that question with a detailed, one-year concept study to examine the planet’s surface, climate, and atmosphere—and to predict its ultimate fate in the solar system.

The mission would allow scientists to better compare Venus with other terrestrial planets—including Earth, Mars, and Mercury—as well as planets recently discovered orbiting stars in other solar systems, says CU-Boulder Professor Larry Esposito, science team leader on the Venus mission proposal.

While Venus and Earth were similar at birth, Venus has since turned into “Earth’s evil twin” because of its extremely harsh and inhospitable conditions, says Esposito.

The concept study to land a spacecraft on Venus is one of three space exploration projects selected as finalists by NASA on Dec. 29 for a $650 million solar system mission to launch no later than 2018. The other proposals selected for further study include one led by the University of Arizona to rendezvous with and orbit a primitive asteroid and one led by Washington University in St. Louis to land near the moon’s south pole and return lunar materials to Earth for study.

“It has been 25 years since a spacecraft last landed on Venus, and our curiosity and scientific capabilities have increased dramatically,” adds Esposito. “This mission will be a big step forward in understanding planetary evolution both in our own solar system and in planetary systems around other stars.”

As part of CU-Boulder’s proposed Surface and Atmosphere Geochemical Explorer, or SAGE mission, the lander would descend onto the flank of an active volcano on Venus known as Mielikki Mons, which is about 200 miles across and 4,800 feet in altitude.

Once the lander was in place, instruments on the spacecraft would dig down about four inches into the surface, then zap the soils with two lasers and a vacuum tube shooting large pulses of neutrons, which would bounce back data to the lander with information on the surface composition and texture, explains Esposito.

The lander would be constructed to survive the harsh conditions on Venus for three hours or more, says Esposito, a professor in the astrophysical and planetary sciences department. “Venus has gone terribly bad since it first formed,” he notes. “The surface pressure is 100 times that of Earth and its temperature is similar to that of a self-cleaning oven. We are very interested in what sent Venus down this hellish path, including its runaway global warming.”

Venus also has a toxic atmosphere filled with carbon dioxide gases and acid rain, he points out. “Understanding the physical and chemical reasons for this uncontrolled warming may help scientists better understand the eventual fate of Earth.”

Instruments proposed to fly on SAGE include a flyby camera, temperature, pressure, dynamics and wind speed hardware, a tunable laser spectrometer to measure stable isotope ratios and a neutral mass spectrometer to measure gases. The lander also would carry descent and panoramic cameras, a microscopic camera, a neutron-activated gamma ray spectrometer and a third spectrometer to measure surface and subsurface composition minerals and elements.

“The minerals that make up the Venus upper crust are still unknown,” says Esposito. “The new information would allow our scientific team to better compare Venus to the other terrestrial planets in our solar system and beyond.”

The proposed Venus mission will build on data collected by the European Space Agency’s Venus Express Mission, an orbiter launched in 2005 that is carrying a camera, two spectrometers, a radio science experiment, and a space plasma and atom-detecting instrument. Esposito, who is a co-investigator of the European mission, says Venus Express has detected several volcanoes with possible recent lava flows, and data from the mission was used to select the proposed landing site for the CU-Boulder mission.

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