Even when we bask in the knowledge that our neighboring planet Mars is currently home to a host of still-functioning landers, a triplet of rovers and with an ever-growing satellite network as well as the first ever flying drone on another planet, our other neighboring planet Venus playing real marigold, with Japan’s Akatsuki orbiter as the lone active Venusian mission right now.
However, that is about to change as NASA has selected two new missions that will explore Venus by the end of this decade. DAVINCI + and VERITAS missions aim to characterize Venus’ atmosphere and map its surface in unprecedented detail, respectively. This should give us information about possible tectonic activity as well as details about the Venusian atmosphere, which has been much missed so far.
Despite the fact that Venus is the closest match to our planet Earth, how is it possible that we have neglected it for so long, and what can we expect from future missions, including and beyond these two new NASA missions?
It was not always like that
In the 1960s, a total of 18 missions from the United States and the USSR targeted at Venus experienced five successful missions:
- Mariner 2 (1962, Flyby)
- Venera 4 (1967, atmospheric)
- Mariner 5 (1967, Flyby)
- Venera 5 (1969, atmospheric)
- Venera 6 (1969, atmospheric)
The exploration continued into the 1970s with 11 Venus missions beginning with the lander Venera 7, which was the first soft landing on another planet, soon followed by the Venera 8 lander. When the 1980s were in full swing, the Venera 13 lander was the first to send audio recordings back from the surface of Venus. But by the time the Vega 2 mission reported its successful landing in 1984, the Soviet Union, which had run the Venera and Vega programs, had stopped exploring Venus. Yet the 1980s saw 8 Venus missions.
By this time, the closest a non-Soviet probe had landed on the Venus Pioneer Venus 2 (Pioneer 13) mission from 1978, when it launched a number of probes into the Venusian atmosphere, one of which continued to submit data to a piece time after it had come up to the surface. Following this mission, the 1989 Magellan Orbiter mission was the United States’ next and final Venus mission.
Although the U.S. Galileo mission observed Venus on its way to Jupiter, this was not its primary mission, and none of the following U.S. probes would perform detailed scientific observations of Venus. The Cassini and MESSENGER missions mostly used Venus as a gravity assistant, leaving the 1990s devoid of any Venus mission. It was not until the 2000s that ESA’s Venus Express would visit Venus. Even then, this ESA probe was made from recycled Mars Express components rather than as a dedicated Venus mission.
Since the 2010s, Venus has become the only domain for Japan’s JAXA, where Akatsuki (‘Dawn’) is still in orbit, but beyond that, nothing but telescopes point to our sister planet.
An exciting planet
Venus is the second planet from the sun after mercury, followed by Earth. Its mass is 81.5% of the soil, 85.7% by volume and ~ 90% by surface area. Its gravity is 8.87 m / s2 compared to 9.80665 m / s2 for the Earth. By comparison, Mars has 15.1% of the Earth’s volume and 28.4% of its surface area with a surface weight of 3.72076 m / s2 which is just over double the Earth’s moon (1.62 m / s2). Effectively, this means that a human on Venus would weigh almost as much as on Earth, and the planet itself is only slightly smaller than Earth.
Venus also has a very dense atmosphere (9.2 MPa), much more than Earth (~ 101,325 kPa at sea level) and a molten core. But for unknown reasons, Venus does not generate a magnetic field using the nucleus’ dynamo, as is the case on Earth. The exact state of Venus’ core, and whether it has a (molten core) dynamo that could function again if the right conditions (eg sufficient convection) were met, remains an active topic for research. All we know at this point is that Venus’ only magnetic field is generated due to the interaction between its ionosphere and the solar wind.
Exactly why Venus has such a dense atmosphere is also unknown. Its atmosphere consists of 96.5% CO2, with nitrogen and trace elements constituting the remainder of the composition, including water vapor (20 ppm). The relatively high levels of sulfur dioxide in the air (150 ppm) combined with the water vapor make clouds of sulfuric acid that protect the planet’s surface from terrestrial telescopes and also give it a yellowish glow. It has been suggested that Venus’ atmosphere is the result of a growth current (atmospheric warming) effect, but future research will have to confirm or disprove this theory.
Also fascinating about Venus is that its axial rotation is opposite to that of Earth, Mars and all other planets in the solar system besides Uranus. This means that the sun on Venus rises in the west and sets in the east. Its rotational speed is also significantly lower than for other planets at 224.7 Earth days. All of this raises many questions about why Venus ended up in such a different state compared to Earth, when evidence suggests that both planets have started much more alike.
Most recently, studies of Venus’ atmosphere using terrestrial measurements have suggested that high levels of phosphine are present in its upper levels, which would be a clear sign of organic life. These can be microbial life forms found in the upper regions of the atmosphere. Despite the fact that the initial phosphine discoveries have been refuted by other scientists, a recent follow-up rejection of refutal confirms these phosphine levels and thus the exciting possibility of life that exists on Venus.
New Venus missions
So far, the 2020s seem to have a bit of a revival in Venus missions with five planned missions:
Not much is known about Rocket Labs’ proposed Venus mission, except that it would probably involve atmospheric measurements. Meanwhile, India Shukrayan-1 mission comes on the heels of its successful Chandrayaan (Lunar) and Mangalyaan (Mars) programs. This mission is likely to complement the VERITAS mission and possibly DAVINCI + if the proposed atmospheric probe is added.
VERITAS ‘main mission has been selected for NASA’s Discovery program and consists of measuring surface emissivity along with using its synthetic aperture radar (SAR) to create the most detailed topographic map of Venus’ surface to date. It will also carry the new Deep Space Atomic Clock-2, whose extra precision will be used to hopefully detect gravity functions in Venus using Doppler displacement of the signal between VERITAS and Earth.
In the meantime, DAVINCI +’s mission will be to measure properties of the atmosphere that its descent probe will throw through, in addition to creating high – resolution photographs of features of the landscape. In particular, the mission plans to collect more data on tesserae, which can be considered equivalent to Earth’s plate tectonics.
The new installment in Russia’s revival of the Venera program in the form of Venera-D is perhaps the most ambitious of all these missions. In addition to repeating the Venera 13 & 14 mission profiles with the landing of a probe on Venus, it will also include an orbiter, and talks are underway with NASA to include the VAMP aircraft (Venus Atmospheric Maneuverable Platform). The latter is a proposal from Northrop Grumman and L’Garde on what would essentially be a long-range aircraft capable of navigating the upper parts of Venus’ atmosphere for up to a year.
If VAMP were to be part of the Venera-D mission, it would allow for the first detailed exploration of this part of Venus’ atmosphere during a month-long mission, giving us the best chance at this point to discover the source of the suspected phosphine and possibly life on Venus.
The Final Frontier
Although these new missions will still take a number of years to realize, with most likely not reaching Venus before the 2030s, the potential of what we can learn not only about Venus but also Earth is simply too tempting. Even beyond figuring out what makes Venus cross, or rather what made it take such a different course from Earth, it’s probably one of the easiest planets we could colonize, for not to mention terraform.
In the coming decades, we can hopefully look forward to the first Venusian rovers as NASA’s Zephyr and AREE concepts. Rovers like these may arrive before or around the time when concepts like HAVOC for floating colonies in Venus’ atmosphere become a reality. The advantage of these would be that the Venusian atmosphere at about 55 km altitude has about the same pressure as on Earth at sea level with a temperature of about 27 ° C (80 ° F).
Whether all of this will really materialize in the coming decades is, of course, anything but certain, not to mention heavily dependent on the policies and budget sizes of the relevant space nations. Here’s a happy note that Europe’s ESA has announced a new Venus orbiter mission in the 2030s, called EnVision. When a manned mission to Venus is announced, it will likely feel like a consolation to those who had been waiting for Venus’ 1973 astronaut flight using a Saturn V rocket.
Here is an exciting new chapter in human history and scientific exploration.