As the EnVision mission to Venus is preparing for its planned launch in 2032, we speak to the Imperial researcher who is a part of the Science Team.
With its extremely high temperatures and surface veiled by thick clouds, Venus represents an unusual example of planet formation and evolution. Once thought to be a tropical paradise, it was only in the 1960s that scientists were able to observe its hostile environment. Despite successful recent missions to the planet, key questions about its atmosphere and geology remain unanswered.
EnVision is a proposed international orbiter mission competing for the European Space Agency’s next launch opportunity in 2032, which seeks to increase our understanding of Venus. Dr Philippa Mason , scientist in the Department of Earth Science and Engineering , is a part of the mission’s Science Team.
As a remote sensing geologist, Philippa uses satellite images to understand the surface processes, tectonics, structure and geology of Earth and other planets.
In our interview, she talks about the research challenges posed by the Venusian environment, her work on EnVision and hopes for the future of Venus exploration.
Read more about our missions to Venus and other planets from the Imperial in Space website and interactive infographic below:
Earth and Venus are sometimes called planetary twins. What are the reasons for this and what do we know about why they have evolved so differently despite their similarities?There are several terrestrial planets in the solar system and Venus and Earth are the most similar in terms of size, density, mass and gravity. It is generally accepted that in the first billion or so years of their life, when they were hot, molten, juvenile planetary bodies, these two planets (and probably Mars and Mercury as well) were very much alike; what then caused their paths to diverge is a subject of great scientific interest and active research at the moment.
Venus is much hotter and much more unpleasant; it probably had water at one stage, but it has lost it. It no longer has a magnetic field and its atmosphere has suffered a runaway greenhouse effect. These are all characteristics which probably represent the future for Earth, but hopefully not too soon!
It has been suggested that the differences between the two planets was merely due to Venus being slightly closer to the Sun than Earth. However, the more we understand the intricate balance between plate tectonics and the recycling of water and carbon dioxide on Earth, the more we realise that the role of geology is more significant.
What do you think would surprise people about Venus?Just over a hundred years ago, when composer Gustav Holst wrote the Planets suite, the astrological Mars represented the bringer of war and Venus the bringer of peace. Since then, we’ve discovered that these roles should have been reversed! Not only is Venus 460 degrees Celsius at the surface (a temperature hot enough to melt lead), but its atmosphere is also 92 times the density of our atmosphere. As a result, being on the surface would be like being in an extremely hot, deep sea, with winds which are much more like ocean currents and strange chemical compounds produced by weathering of metals, stable at different pressures and temperatures. Another surprising fact is that Venus spins very slowly and in the opposite direction to every other planet. It takes longer for it to turn on its axis once than it does to go around the Sun, making a day on Venus longer than a year.
Space agencies have long overlooked Venus in favour of exploring other planets. Why do you think this is?I think there are a variety of reasons. Magellan, launched by NASA in 1989, was one of the few planetary missions to Venus in the past thirty years. That one orbiting visit, and the images it provided, led scientists believe that Venus was dead, and not geologically active at all - it was sort of accepted that there was little more to study.
It is only recently that studies into the dynamics of early planetary processes on Earth and the mechanisms of plate tectonics have made us realise that we needed to look at Venus again to find an explanation for all the complexity we see on that planet.
Furthermore, Venus is quite a difficult environment to image. The planet’s thick atmosphere means that we cannot use optical cameras, only radar images and these do not capture people’s imagination in the same way that the beautiful high resolution images of Mars do. Certainly, in the past ten years, everybody’s “gone mad” with Mars. Mars having almost no atmosphere and it being cold means that it is much easier to image from orbit and to land and examine it closely. This doesn’t mean that we shouldn’t go to Venus, but these factors certainly make it more difficult to gain support for a mission.
Why is there renewed interest in the planet?The European Space Agency’s Venus Express mission , which finished in 2014, made some really important discoveries about the planet’s atmosphere. Firstly, it found that its sulphur dioxide content is dynamic, suggesting that volcanoes are erupting and putting a lot of gas into the atmosphere. Secondly, it detected hot spots on the surface over known volcanoes, which indicates that they are active now, and that something is driving that volcanism inside the planet. What we don’t yet understand is the mechanism and the frequency of eruptions.
These very important discoveries - telling us that Venus is very much alive - are some of the key reasons why need to go back there. Coupled with the current work in understanding early Earth and its processes, they make us realise that we need to understand more about the planet, because it is intricately linked with our future on Earth. There are climate lessons to learn, as well as geological lessons.
What are the unique challenges faced by scientists in Venus exploration?It is hot, dense and difficult to land on, which means that missions have to orbit around to observe it. However, it’s also difficult to put a spacecraft in a nice circular orbit, because Venus’s topography and its mass make keeping the spacecraft in that orbit very programmatically expensive, and this is a complex issue for engineers to solve.
The Russians landed a number of spacecraft (the Venera Landers) on the surface in the 1970s and 1980s and these robust metal structures were designed to last about half an hour. They landers captured a series of ground level images and conducted some in situ tests, and their sensors actually lasted about two hours before they gradually succumbed to the intense heat and pressure. We don’t know yet what advances we can make in this respect in the next ten years.
What is the EnVision mission aiming to find out about Venus and what is Imperial’s contribution to the mission?EnVision aims to demonstrate that Venus is alive and active by showing and quantitatively measuring how much change is occurring on the surface of the planet. We want to explore the effect winds have on the surface and what the materials on the surface are like. By imaging at different radar polarisations, we may be able to distinguish between granular and solid surface materials, while infrared images (in certain parts of the spectrum where the atmosphere is semi-transparent) can help to determine what these materials are made of (for example, whether they contain oxidised iron, or if they are like basalts or more like granites).
In addition, we will try to show that there are tectonic plate movements. We will image the surface in great detail, and more than once, to be able to demonstrate changes over the course of the mission life time. We will also use a subsurface imaging instrument to tell us about structures below the surface, or the thickness of sediment lying over rocky surfaces.
With an integrated suite of instruments and observations, we will attempt to emulate some of the holistic approaches to data collection that we adopt on Earth, bearing in mind all those difficult physical constraints that we have on Venus.
In the Science Team, I am the lead of Surface Processes; it is my job to think about what images we need, at what resolutions, and where are the areas we need the image, as well as how well will these areas answer some of our science questions.
What stage is EnVision currently in and what are the next steps for the team?Currently we are in what’s known as Phase A Study. Following mission proposal submission and review, three medium-class (M5) missions were selected for Phase A studies. That means three years of instrument testing, feasibility studies and discussion to determine what the Science Team’s goals are and whether our instruments can deliver these, anticipating any problems we might encounter. We then need to report these needs to the engineers, to work out whether they are achievable. It’s a fascinating three-year period of learning, discussion and compromise.
In summer 2021, the European Space Agency will choose among three missions and the selected mission will ultimately be launched in ca 2032. EnVision is the only planetary mission still in the race; the other two, Spica and Theseus, being astronomy missions. To maximise our chances of being chosen, we have to keep pushing and working hard, do as much outreach as we can, raise awareness and grow the community of interested parties. This community very much includes the younger generation who will be mature scientists by the time we start collecting data, as well as those currently working in science who will still be supervising students.
What are your hopes for the future of Venus research?I am hoping to demonstrate that the reasons why Venus is as it is are quite complex and closely linked to the processes we now understand about Earth. I want to show that it’s alive and busy and would like our understanding of Venus to be at a similar level to that of Mars now, and with there being an ongoing programme of missions planned.
Mars obviously has an added interest as we could be looking at people living there in the future, whereas for Venus, that’s a difficult scenario to envisage. Nevertheless I am certainly hoping for a planned programme of scientific missions within the next twenty years to better understand Venus. We don’t expect to launch EnVision until 2032 and we would only start receiving data in 2035. By then, I hope somebody will already be planning the next mission.