Venus remains a major subject of scientific interest, albeit only a minor target for unmanned space missions. Although a large number of Soviet and American probes were despatched to the planet during the Cold War, since the 1990s cash-strapped space agency budgets have resulted in cuts to most of the planetary space probes, except those bound for Mars and Jupiter. Nevertheless, several missions are expected to launch for the planet over the next decade, and more may come if research priorities change and some important technical difficulties are overcome.
In the meantime, relative disinterest by the major space powers means that the leading edge of Venusian research is, for the moment, dominated by new players like Japan and Europe. In fact, the only research mission currently in orbit of Venus, the Venus Express probe, is a project of the European Space Agency, and it is scheduled to be retired once an upcoming Japanese spacecraft, Akatsuki, joins it in orbit.
2010: AKATSUKI (Japan)
In May 2010, the Japanese Aerospace Exploration Agency (JAXA) expects to launch their Akatsuki probe, which will make a six-month trip to Venus and then conduct scientific experiments from orbit for a minimum of two years. Formerly known by the more bland moniker “Planet-C,” Akatsuki is a fairly small probe, less than six feet long in any direction (minus its solar panel array, of course), but carries ultraviolet, infrared, and visual cameras for its orbital research. JAXA hopes that Akatsuki will restore their reputation after their last major project, Planet-B (later renamed Nozomi), failed on its way to Mars in 2003.
Akatsuki’s operators hope the spacecraft will bring new understanding of Venusian weather as well as of the extremely heavy storms which constantly bombard its surface, generating winds of 300 feet per second. These speeds are mysterious because they are far faster than the planet itself rotates: probably due to an unknown cataclysmic collision in its distant past, Venus, which is roughly Earth-sized, has a day more than 220 times as long as ours.
2014: BEPI-COLOMBO (Europe and Japan)
In 2014, the European Space Agency, with assistance from JAXA, plans to launch its BepiColombo space probe, which will follow on the heels of NASA’s Messenger probe, currently en route to the planet Mercury. BepiColombo will finish its mission in orbit of Mercury, like its predecessor, but is scheduled to fly by Venus first. That flyby will give it a chance to test its instruments and send back some photographs.
2016: VENERA-D (Russia)
During the Cold War, the Soviet Union always had considerably greater success in studying Venus than the U.S. did (by contrast, American space probes have usually fared better than Russian ones with respect to Mars). Venera-D represents the Russian return to Venus exploration, and takes its name from the series of 16 Venera probes launched from Russia between the 1960s and 1980s. Like Magellan, the American probe sent to Venus during the 1990s, Venera-D is intended to conduct detailed mapping of the planet’s surface; in this case, it has the specific objective of locating a suitable landing site for a Russian-built unmanned lander.
Unlike the Europeans, the Russians have actually landed spacecraft on Venus before – several of the Venera spacecraft included landers; and Venera 9 sent back the first pictures of another planet’s surface, in 1975. However, several of those landers failed catastrophically during their descent phase, and few survived more than an hour in the lethal 800-Fahrenheit heat of the planet’s parched surface. Future landers would be expected to last somewhat longer in order to justify their greater cost. Scientists want Venera-D, for example, to survive for at least a month.
While Russia’s return to Venus is ambitious, it is also at substantial risk of long delays due to budget cuts. Major success in the country’s upcoming Phobos-Grunt mission to Mars, which will launch by 2012, would probably encourage the Russian government to continue its commitment to Venera-D.
2016-2018: EVE (Europe)
Tentatively scheduled for launch in 2016-2018, the European Venus Explorer (Eve) is a European Space Agency plan to send an orbiter and atmospheric probe to Venus. Originally the Venus Entry Probe, the high point of this mission would be the launch of an “aerobot” complete with a light-gas balloon, which would plummet into the atmosphere, deploy its balloon, and reach a stable cruising altitude of about 30 miles. The minimum expected survival time for the aerobot would be two weeks, enough time – according to our current understanding of Venusian meteorology – to be blown twice around the circumference of the planet.
Europe’s plan is obviously somewhat speculative at this point; if Eve is eventually built, it will very likely only be launched well after the currently proposed launch window.
THE FUTURE OF AMERICAN EXPLORATION
The United States currently has no concrete plans to join the small assortment of probes being sent to Venus. For a time, a major atmospheric probe called the Venus In-Situ Explorer (VISE) was scheduled for development. At present, NASA’s website lists an even more ambitious mission, the Venus Mobile Explorer, which would plummet through the atmosphere, study Venus’s history of drastic climate change, and then land and perform rock studies similar to those already accomplished by the Mars landers.
At present, however, neither project has ever passed beyond the concept stage. In December 2009, NASA announced that the Venus lander was one of three projects which had been selected for the final New Frontiers competition. (The others are a mission to the Moon and a mission to an asteroid.) Assuming some level of funding remains available, one of those projects will be selected for full funding by 2011, and could be launched by 2018.
WHY NOT VENUS?
Future plans, like past programs, afford substantially less attention to Venus than to Mars – which is why the list of future missions to Venus is substantially shorter than those bound for the red planet. There are essentially three reasons. The first and arguably most important is that current science priorities have more to do with Mars than Venus: one of the most important objectives guiding current Mars exploration is the search for water and indicators that microbe life once existed on that planet. In contrast, we learned from Mariner 2 that the surface of Venus is always several hundred degrees above that of Earth – probably too hot for any chance of life ever arising. Different research objectives could lead to renewed interest in Venus in the future, since some scientists believe the planet’s corrosive atmosphere could teach us a great deal about runaway greenhouse effects.
The other two complications are technical rather than scientific. First, it’s simply harder to get there: Mars is much farther away from the Sun, but space probes sent there can rely on the Sun’s gravity to slow them down a little bit prior to their arrival. Probes sent to Venus must carry enough fuel for heavier braking maneuvers at the end of their trip. Second, once they’ve arrived, the atmosphere and surface are much too harsh to permit the long-term rover missions that NASA has sent to Mars; aside from a few minutes of data transmitted by a Soviet lander during the Cold War, all exploration of Venus has so far been from orbit.
