March 5, 1982. A brilliant streak lights up the Venusian sky, but this is no meteor. It is the descent craft of Venera 14, a Soviet mission that seeks to penetrate deep into Earth’s cloud-covered neighbour. The probe is designed for conditions so hellish that there is no parallel environment to be found on its home world. Venera 14 deploys a parachute, and after a four-month journey, it becomes the latest spacecraft to land on Venus. Two lens caps are jettisoned, falling to their fiery end on a surface that is hot enough to melt lead.
57 minutes later, Venera 14 finally succumbs to the crushing Venusian environment. Yet scientists rejoice. After all, 57 minutes is 25 minutes longer than what they anticipated, and in that period, two images are sent back to Earth. Never again would humankind gaze upon Earth’s sister planet from its own surface.
57 minutes later, Venera 14 finally succumbs to the crushing Venusian environment. Yet scientists rejoice. After all, 57 minutes is 25 minutes longer than what they anticipated, and in that period, two images are sent back to Earth. Never again would humankind gaze upon Earth’s sister planet from its own surface.
Venus has attracted the curiosity of humans for generations. Its tendency to shine primarily at dawn or dusk, combined with the fact that it is the third brightest object in the sky has spawned an entire genre of mythology, ranging from the ancient Romans’ belief that Venus was the goddess of love and beauty, to the Venus-based calendar that the Mayans developed. The invention of the telescope only further fuelled our fascination with Venus, as even with such a powerful instrument, the secrets of the planet remained hidden by a visually impenetrable cloud layer. Even as late as the early 20th century, some scientists were convinced that an alien civilization existed on the surface!
However, this was not to be. As more and more probes were launched, our understanding of the Venusian environment drifted further and further from the picture of lush, tropical forests that science fiction writers had been dreaming about for centuries. The more we learned, the lower the habitability got. By the time Venera 14 landed, the conditions on the surface were known, and few scientists held out hope for alien life. The spacecraft only confirmed what other Soviet and American missions had already found before: the brilliant white clouds seen from Earth were not clouds of water vapor, but of sulfuric acid floating in a toxic, torrid atmosphere that produced a surface pressure 90 times that of sea level pressure on Earth. Venus was an inhospitable inferno, and as the possibility of alien life rapidly disappeared, so too did our desire to explore the planet.
Apart from the occasional orbiter and spacecraft flying by to get to another planet, Venus has largely been cast aside in the history of planetary exploration. Its brutal conditions makes expeditions challenging, and the allure of Earth’s other neighbor, Mars, has caused the exploration of Venus to stagnate since the end of NASA’s Magellan mission in 1994. Since then, numerous Venus fly-bys have occurred, but only two spacecraft geared specifically for Venusian exploration have launched: the European Space Agency’s Venus Express, which ended its mission in 2014, and Japan’s Akatsuki orbiter, which has been operational since 2015. While fly-bys are better than nothing, they are quite limited in scope because the primary objective of a Venus fly-by is not to collect scientific data, but rather to perform a trajectory correction maneuver known as a gravity assist.
In essence, a gravity assist allows a spacecraft to change its velocity without using any fuel by relying on an object’s gravity to take control of it for a small amount of time. This is particularly useful for spacecraft heading close to the sun or far away from it, as travel to these locations require tremendous amounts of energy. For instance, NASA and the European Space Agency’s Cassini-Huygens spacecraft flew past Venus twice to get to Saturn, while NASA’s Parker Solar Probe will conduct 7 Venus fly-bys in 7 years in order to achieve a tight orbit around its primary target, the sun.
However, the tendency to send spacecraft to Venus for logistical reasons is beginning to shift, paving the way for a new wave of Venusian exploration. The planet is once again in the spotlight, and space agencies around the world are now planning for a triumphant return to the planet we have neglected for so long.
On June 2nd, 2021, NASA provided the biggest boost to the exploration of Venus in decades by announcing not one, but two missions that will head to the planet as part of the agency’s Discovery Program. The first to launch in 2028 will be the VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) orbiter, which will be followed by the DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging, Plus) atmospheric probe a year later. Eight days later, on June 10, the European Space Agency announced that it too would send a mission: EnVision, a Venus orbiter scheduled to launch in the early 2030s. Alongside these governmental missions, Rocket Lab, a commercial spaceflight company, has also expressed its intention to launch a private Venus mission by 2023. Yet there may be even more in store for Venus in this decade, as the Russian space agency, Roscosmos, has also been planning a return to the surface of Venus as early as 2029 with its Venera-D mission (a successor to the Soviet line of Venera probes). After all these announcements about Venus missions, one question begs to be answered: Why?
To begin, we look toward another planet: Mars. This world has been the focus of planetary exploration for much of history particularly because, like Venus, it's relatively easy to get to, and opportunities to launch for Mars come fairly often at a little more than every two years. Perhaps one of the biggest reasons is the possibility that Mars once harbored liquid water, and maybe life, just like Earth does now. Yet, this attention to Mars has left a Venus sized vacuum in our understanding of the solar system, which is problematic because Venus offers us an exclusive opportunity to explore a planet that is remarkably similar to Earth in terms of size, mass, and evolution. In fact, Venus lies in the inner regions of the Sun’s habitable zone, which means that even if water doesn’t exist on the planet’s surface today, it may have once been there in the past. Some scientists have speculated that Venus may have had oceans of liquid water, and perhaps life as recently as 700 million years ago. This possibility forms one of VERITAS and EnVision’s mission objectives, as they both seek to find out whether the surface could have had water on it in the past.
Another hint to the possibility of life emerged in late 2020, when scientists detected traces of phosphine, a gas that, on Earth, is produced by living organisms and volcanic eruptions. Since phosphine breaks down rapidly, the discovery suggested that either volcanic eruptions, alien life, or some unknown natural process on Venus is constantly replenishing the supply of the gas. The quest to solve this mystery is just another reason why Venus exploration is making a comeback.
But the fact that Earth and its twin went down completely different paths also prompts the question: “How did Earth and Venus, despite being so similar, end up so different?” This is the ultimate question that is guiding our exploration of Venus, and it is all the more important with the emerging climate crisis here on Earth. After all, there is no better place where we can see the effects of a runaway greenhouse gas effect, and it is possible that Venus will provide us with the information we need to defeat the existential threat that humanity faces. Whatever the outcome, there is no doubt that Venus is a window into one of the many futures that may be ahead of Earth.
From decades of scientific exploration we now know that there was most likely a period of time when there were perhaps not one, not two, but three pale blue marbles in the early Solar System. Yet this distant reality differs sharply from the one we live in today, as Mars became a cold, dead world, and Venus became a choking hell, while Earth remained a watery paradise. Why this occurred is unknown to us, but it is something that we must find out, because the answer could completely reshape our knowledge on how the Solar System evolved, and what will happen to it next. Leaving Venus out of this puzzle will keep a third of the pieces invisible, but thankfully, the planet has come back with a vengeance, and VERITAS, DAVINCI+, EnVision, and other future missions will be critical to catching up with what we have missed on the clouded world so far. Perhaps, exploring Venus will allow us to see that even in such a hellish place, there is much to be learned.