Two balloons, two landers, and an orbiter could be sent together to Venus in a major ‘flagship’ mission (Image: NASA/JPL) An aluminium-coated balloon that could be used to explore Venus for weeks is being tested at NASA’s Jet Propulsion Laboratory (Image: NASA/JPL)

Two high-altitude balloons built to hover in sulphuric acid clouds could be part of a future fleet of spacecraft sent to Venus, a NASA advisory team says.


The multi-billion-dollar mission concept – which is being considered for launch in the next fifteen years – could help reveal more about Venus’s runaway greenhouse effect, any oceans it may once have had, and possible ongoing volcanic activity.

It could be the next flagship mission sent to a planet, after a planned mission to Jupiter and its moons set for launch in 2020.

The Venus mission would cost some $3 billion to 4 billion and would launch between 2020 and 2025, according to NASA, which in 2008 tasked a group of scientists and engineers to formulate goals for the mission.

The team’s study, which will be released in April, outlines a plan to study the hazy planet, which has more in common with Earth than any other in terms of distance from the Sun, size and mass, but evolved into an inhospitable world where surface temperatures hover close to 450°C and sulphuric acid rains from the sky.

The team’s mission concept includes one orbiter, two balloons and two short-lived landers, all of which would launch into space on two Atlas V rockets.

“Our understanding of Venus is so low, we really need this armada,” says planetary scientist Mark Bullock of the Southwest Research Institute in Boulder, Colorado, one of the team leaders.

Signs of water

As an ensemble, the spacecraft could help reveal what happened to Venus’s oceans. Researchers believe water was once plentiful enough to have been able to cover the entire planet in a layer 100 metres deep.

But Venus’s hothouse climate eventually dried up most of this water, a process that might have also slowed and eventually stopped plate tectonics on the planet.

The landers, which would only last a few hours in the intense heat, could look for evidence of minerals formed by water. Since such hydrated minerals have a limited lifetime, they could help reveal how long Venus’s oceans might have lasted, a question that could shed light on whether life might have arisen on the planet.

Long-lived balloons

The mission’s two balloons would each carry a gondola full of scientific instruments to sniff the atmosphere at an altitude of 55 kilometres.

The last balloons to study Venus, sent by the Soviet Union, descended into the planet’s hazy atmosphere in 1985. Each is thought to have lasted just a few days. But the NASA balloons could be designed to last for a month, enough time for each to circumnavigate the planet seven times.

The mission could also help reveal more about the origin of Venus’s current carbon dioxide atmosphere, which produces crushing surface pressures 90 times those on Earth.

Cataclysmic impact

It’s unclear whether the planet once lost much of its atmosphere in a cataclysmic impact, like the Earth did in the impact that formed the Moon, later replenishing it with volcanic activity, or whether it has held onto its original atmosphere.

The balloons and descending landers could study this by measuring isotopes of xenon, an unreactive gas that is relatively heavy and therefore should stay put in the atmosphere, barring any violent impacts. If lightweight isotopes of the gas are relatively abundant, that would suggest that the planet has held onto much of its original atmosphere.

The balloons would also be test particles that could be used to track Venus’s super-fast winds, which, for reasons that are still not understood, move around the planet 60 times faster than the planet’s surface rotates.

Active volcanism

The orbiter could reveal whether geological activity continues on the planet, by looking for bulges on the surface that could signal ongoing volcanic activity.

This activity has been hinted at by the presence of sulphuric acid in the atmosphere, but never seen. Venus boasts the most volcanoes of any planet in the solar system, and nearly 90% of its surface is covered by basaltic lava flows. Finding ongoing volcanic activity in certain spots would help account for the planet’s extreme climate.

Although such a mission is at least a decade away, preliminary work may need to begin now. “Because it’s such a challenging mission, we are going to recommend NASA begin investing in the required technology right away,” Bullock told New Scientist.

Balloon tests

At NASA’s Jet Propulsion Laboratory, research is already being done in the hopes of eventually getting funding to launch a smaller balloon-only mission to Venus, called VALOR.

The balloon is made of high-strength polymers and coated with aluminium to deflect most of the Sun’s radiation, which could cause the balloon to heat up and burst. A layer of Teflon protects the balloon from sulphuric acid in Venus’s atmosphere.

Later this year, the team is planning its first in-air deployment of the balloon. A helicopter will be used to carry the folded-up prototype to an altitude of 2 to 3 kilometres, where it will be released and inflated with helium while dropping to Earth beneath a parachute.