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Even as we rejoice to know that our neighboring planet Mars is currently home to a multitude of still functional landers, a triplet of rovers and with an ever-growing network of satellites as well as the very first drone to fly on another planet, our other neighbor planet Venus is really playing wallflower, with Japanese orbiter Akatsuki as the only active Venusian mission at the moment.
That is about to change, however, with NASA having selected two new missions that will explore Venus by the end of this decade. The DAVINCI + and VERITAS missions aim respectively to characterize the atmosphere of Venus and to map its surface with unprecedented precision. This should provide us with information on possible tectonic activity, as well as details of the Venusian atmosphere that so far have been sorely lacking.
Although 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 missions from the NASA?
It wasn’t always like this
The 1960s saw a total of 18 US and USSR missions that targeted Venus, with five missions successfully completed:
- Mariner 2 (1962, Overview)
- Venera 4 (1967, Atmospheric)
- Mariner 5 (1967, overview)
- Venera 5 (1969, Atmospheric)
- Venera 6 (1969, Atmospheric)
Exploration continued into the 1970s with 11 Venus missions starting with the Venera 7 lander, which was the first soft landing on another planet, soon followed by the Venera 8 lander. 1980 was in full swing, the Venera 13 lander was the first to return recorded audio from the surface of Venus. Yet, by the time the Vega 2 mission announced its successful landing in 1984, the USSR which ran the Venera and Vega programs ceased its exploration of Venus. Even so, the 1980s saw 8 Venus missions.
At this point, the closest mission to a non-Soviet Venus probe was the 1978 Pioneer Venus 2 (Pioneer 13) mission when it launched a number of probes into the Venus atmosphere, one of which has continued to submit data for some time after it had come to the surface. After this mission, the 1989 Magellan Orbiter mission was the next and last US mission to Venus.
Although the US Galileo mission observed Venus on its way to Jupiter, that was not its primary mission, and no subsequent US probe would make detailed scientific observations of Venus. The Cassini and MESSENGER missions both primarily used Venus for gravitational assistance, leaving the 1990s devoid of any Venus mission. It wasn’t until the 2000s that ESA’s Venus Express would visit Venus. Even then, this ESA probe was made from reused Mars Express components rather than a dedicated Venus mission.
Since the 2010s, Venus has become the exclusive domain of Japanese JAXA, with Akatsuki (“Dawn”) still in orbit, but beyond, nothing but telescopes pointed at our sister planet.
A fascinating planet
Venus is the second planet from the Sun after Mercury, followed by Earth. Its mass is 81.5% that of the Earth, 85.7% by volume and ~ 90% by surface. Its surface gravity is 8.87 m / s2 against 9.80665 m / s2 for Earth. In comparison, Mars has 15.1% of the Earth’s volume and 28.4% of the surface, with a surface gravity of 3.72076 m / s2 which is a little more than double that of Earth’s Moon (1.62 m / s2). In fact, this means that a human on Venus would weigh almost as much as on Earth, and the planet itself is only a little smaller than Earth.
Venus also has a very dense atmosphere (9.2 MPa), much larger than Earth (~ 101.325 kPa at sea level), and a molten core. Yet, for unknown reasons, Venus does not generate a magnetic field using the core dynamo, as it does on Earth. The exact state of the nucleus of Venus and whether it has a dynamo (molten nucleus) that could work again if the right conditions (eg sufficient convection) were met remains an active topic of research. All we know at this point is that Venus’s only magnetic field is generated due to the interaction between its ionosphere and the solar wind.
The exact reason why Venus has such a dense atmosphere is also unknown. Its atmosphere is composed of 96.5% CO2, with nitrogen and trace elements composing the rest of the composition, including water vapor (20 ppm). The relatively high levels of sulfur dioxide in the air (150 ppm) combined with water vapor create clouds of sulfuric acid which protect the planet’s surface from terrestrial telescopes and also give it a glow yellowish. It has been suggested that the atmosphere of Venus is the result of an uncontrollable greenhouse effect (atmospheric warming), but future research will need to confirm or refute this theory.
What’s also fascinating about Venus is that its axial rotation is opposite that of Earth, Mars, and all the other planets in the solar system besides Uranus. This means that on Venus, the Sun rises in the west and sets in the east. Its rotational speed is also significantly lower than that of other planets at 224.7 Earth days. All of this raises many questions as to why Venus ended up in such a different state from Earth when the evidence points to the two planets starting out much more similar.
More recently, studies of Venus’ atmosphere using terrestrial measurements have suggested that high levels of phosphine exist in its upper levels, which would be a clear sign of organic life. It could be microbial life forms existing in the upper regions of the atmosphere. Although the initial findings on phosphine have been refuted by other researchers, a recent follow-up rebuttal of the rebuttal reaffirms these phosphine levels and therefore the tantalizing possibility of life existing on Venus.
New missions of Venus
So far, the 2020s seem to present a certain revival in the missions of Venus, with five missions planned:
Little is known about the Venus mission proposed by Rocket Lab, other than the fact that it would likely involve atmospheric measurements. Meanwhile, India Shukrayan-1 The mission follows the success of its Chandrayaan (Lunar) and Mangalyaan (Mars) programs. This mission is likely to be complementary to the VERITAS mission, and possibly DAVINCI + if the proposed atmospheric probe is added.
Selected for NASA’s Discovery program, VERITAS ‘main mission is to measure the emissivity of the surface and use its Synthetic Aperture Radar (SAR) instrument to create the most detailed topographic map of the surface of Venus nowadays. It will also carry the new Deep Space Atomic Clock-2, the added precision of which will hopefully be used to detect the gravitational characteristics of Venus using the Doppler shift of the signal between VERITAS and Earth.
At the same time, DAVINCI + ‘s mission will be to measure the properties of the atmosphere in which its descent probe will immerse, in addition to creating high resolution photographs of the elements of the landscape. In particular, the mission plans to collect more data on the tesserae, which can be considered equivalent to terrestrial plate tectonics.
Perhaps the most ambitious of all these missions is the new installment of the Russian revival of the Venera program in the form of Venera-D. In addition to repeating the Venera-13 and 14 mission profiles with the landing of a probe on Venus, it would include an orbiter and talks are underway with NASA to include the VAMP (Venus Atmospheric Maneuvable Platform) aircraft. The latter is a proposal by Northrop Grumman and L’Garde for what would essentially be a long-duration 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 the first detailed exploration of this part of Venus’ atmosphere in a multi-month mission, giving us at this point the best chance of discovering the source of the suspect phosphine and possibly life on Venus.
The final frontier
While these new missions still take a number of years to materialize, with most of them likely not reaching Venus until the 2030s, the potential for what we can learn not only about Venus, but also about Earth is just too tempting. Even beyond understanding what makes Venus vibrate, or perhaps rather what caused her to take such a different course from Earth, this is probably one of the easiest planets we can colonize, not to mention the terraform.
Over the next several decades, we can hopefully expect early Venusian rovers such as NASA’s Zephyr and AREE concepts. Rovers like these can arrive before or around the time concepts like HAVOC for floating colonies in the atmosphere of Venus become a reality. The advantage of these would be that at about 55 km altitude, the Venusian atmosphere has about the same pressure as on Earth at sea level, with a temperature of about 27 ° C (80 ° F).
Whether or not this will materialize over the next few decades is of course anything but certain, not to mention the heavy reliance on politics and the size of the budgets of the space nations involved. Here, a happy note is that ESA in Europe announced a new Venus Orbiter mission in the 2030s called EnVision. When a manned mission to Venus is announced, it will likely be a consolation for those waiting for the astronaut to fly over Venus in 1973 using a Saturn V rocket.
Here is an exciting new chapter in human history and scientific exploration.
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