What can Venus atmospheric samples returned to Earth teach us about the varied evolution of both planets? This is what a recent study presented at the American Geophysical Union (AGU) Fall 2024 Meeting discussed a compelling mission concept called VATMOS-SR (Venus ATMOSphere – Sample Return), which is designed to collect samples from Venus’ atmosphere and return them to Earth for further study. This mission has the potential to help scientists gain greater insights into the formation and evolution of Venus and how it diverged so far from Earth’s evolution, despite both planets being approximately the same size.
Here, Universe Today discusses this incredible mission concept with Dr. Guillaume Avice, who is a National Centre for Scientific Research (CNRS) Permanent Researchers at the Paris Institute of Global Physics and lead author of the mission concept, regarding the motivation behind VATMOS-SR, advantages and limitations, significant results they hope to achieve with VATMOS-SR, steps being taken to address specific sampling concerns, nest steps in making VATMOS-SR a reality, and what can VATMOS-SR potentially teach us about finding life in Venus’ atmosphere. Therefore, what was the motivation behind the VATMOS-SR mission concept?
“The scientific motivation concerns the origin and evolution of planetary atmospheres,” Dr. Avice tells Universe Today. “We know very well the Earth’s atmosphere and we have some insights about the ancient Earth’s atmosphere. For Venus, there are measurements done in the 70’s but we have only very partial data. Returning a sample from the Venus atmosphere would allow us to put strong constraints on the delivery of volatile elements to terrestrial planets soon after solar system formation. Indeed, the two planets are very similar in terms of size, position relative to the Sun etc. Yet, their respective evolution diverged, and it remains a mystery why. Another motivation is that we would return for the first time (if we do it before Mars Sample Return) a sample from another planet than Earth.”
For VATMOS-SR, the researchers aim to accomplish three primary scientific objectives: the sources of volatile elements in Venus’ atmosphere, comparing today’s number of volatile elements to when they first formed billions of years ago, and examining the gases that transferred from Venus’ interior to its atmosphere throughout the planet’s history (also called outgassing). To accomplish this, VATMOS-SR is designed to collect several atmospheric liter-sized samples approximately 110 kilometers (68 miles) above the surface of Venus while traveling at more than 10 kilometers per second (6 miles per second).
VATMOS-SR builds off a previous mission concept called Cupid’s Arrow, which was presented at the 49th Lunar and Planetary Science Conference in 2018, with the primary difference being VATMOS-SR will return the samples to Earth whereas Cupid’s Arrow was slated to analyze the samples while still at Venus. Like all mission concepts, the authors note there are advantages and limitations for VATMOS-SR.
“The great advantage is that instruments in our laboratories are very precise for determining the abundance and isotopic composition of volatile elements,” Dr. Avice tells Universe Today. “This is a much better situation compared to in-situ measurements by an instrument onboard a space probe which has numerous limitations. The limitation of the mission is that, in order to return the sample back to Earth, sampling will happen at high velocity (10-13 km/s) meaning that the gas will be fractionated. We can correct for this effect but this is a limitation of the mission. Another one is that sampling gas means that measurements have to be done quickly when back on Earth because any sampling device you could imagine will have a leak rate. We can use high-tech technology to preserve the gas but ideally the preliminary science will have to be done quickly after return.”
As noted, Earth and Venus are approximately the same size, with Venus’s diameter approximately 95 percent of Earth’s. Despite this, both planets are starkly different regarding their characteristics, specifically surface temperatures and pressures. While Earth’s average surface temperature is a livable 15 degrees Celsius (59 degrees Fahrenheit), Venus’s average surface temperature is a scorching 462 degrees Celsius (864 degrees Fahrenheit), which is hot enough to melt lead.
While Earth’s average surface pressure is measured at 14.7 pounds per square inch (psi), Venus’ average surface pressure is approximately 92 times higher, which is equivalent to experiencing the pressures at 900 meters (3,000 feet) underwater on Earth. This is due to Venus’ atmosphere being extremely dense and composed of carbon dioxide (~96.5 percent), leading to a runaway greenhouse effect. In contrast, while the atmosphere of the planet Mars is also composed of largely carbon dioxide (~95 percent), its atmosphere is much thinner, resulting in significantly lower average surface pressure. Therefore, despite the vast differences between Earth and Venus, what are the most significant results the team hopes to achieve with VATMOS-SR?
“To understand the origin and evolution of the atmosphere of Venus to better understand Earth’s sister planet but also to understand what makes a planet habitable or not,” Dr. Avice tells Universe Today. “This is also extremely important to understand exoplanets because atmospheres of exoplanets are the only reservoir that can be measured remotely with telescopes. Understanding exoplanets thus requires to understand the composition of planetary atmospheres in our solar system.”
Regarding the fractionation concerns about obtaining the samples at such high speeds, Dr. Avice notes statistical studies have been conducted in collaboration with NASA showing promising results and notes the next steps will involve similar tests but with better probe designs.
Going from a concept to becoming an actual mission and delivering groundbreaking science often takes years to decades to happen, often involving several stages of ideas, scientific implications, systems analysis, designs, prototypes, re-designs, and funding availability. Once components and hardware are finally built, they are tested and re-tested to ensure maximum operational capacity since they can’t be fixed after launch. This ensures all systems function independently and together to achieve maximum mission success, including science data collection and transmitting data back to Earth in a timely and efficient manner.
For example, while NASA’s New Horizons spacecraft conducted its famous flyby of Pluto in July 2015, the mission concept was first proposed in August 1992, accepted as a concept in June 2001, received funding approval in November 2001. It was finally launched in June 2006 and endured a 9-year journey to Pluto where it sent back breathtaking images of the dwarf planet in July 2015. Therefore, what are the next steps to making VATMOS-SR a reality?
Dr. Avice tells Universe Today, “We gathered a European team of scientists and engineers together with American and Japanese colleagues to propose VATMOS-SR to the coming ESA call for F-class (fast) mission. The CNES (French space agency) is supporting VATMOS-SR and is providing a lot of help with engineers and specialists to build a strong case to answer this call. This call will be released next month and, if selected, VATMOS-SR will be under consideration by the European Space Agency with developing activities starting as soon as 2026.”
The VATMOS-SR concept comes as debate continues to rage regarding whether the atmosphere of Venus is capable of hosting life as we know it, since the upper atmosphere has been shown to exhibit Earth-like temperatures and pressures, which is a stark contrast to the surface of Venus. It is estimated that the habitable zone of Venus’ atmosphere is between 51 kilometers (32 miles) and 62 kilometers (38 miles) above the surface that exhibit temperatures between 65 degrees Celsius (149 degrees Fahrenheit) and -20 degrees Celsius (-4 degrees Fahrenheit), respectively. As noted, VATMOS-SR is slated to collect samples at approximately 110 kilometers (68 miles) above the surface, or more than twice the altitude from the estimated atmospheric habitable zone. Despite this, what can VATMOS-SR teach us about finding life in Venus’ atmosphere?
Dr. Avice tells Universe Today, “Nothing directly (and no chance to have live organisms in the gas samples) but VATMOS-SR will tell us why Venus became such an inhabitable place. This is of course linked to the question, ‘Is it possible that life appeared on Venus at some point in its history?’”
For now, VATMOS-SR remains a very intriguing mission concept with the goal of helping us unravel the history of Venus and potentially the solar system, along with being an international collaboration between the United States, Europe (CNES), and Japan. While Dr. Avice is designated as the principal investigator, it was Dr. Christophe Sotin, who is a Co-PI, professor at the University of Nantes, former senior research scientist at NASA JPL, and lead author of the Cupid’s Arrow study, who first proposed measuring Venus’ atmosphere.
What new insights into Venus’ evolutionary history could VATMOS-SR provide scientists in the coming years and decades? Only time will tell, and this is why we science!
As always, keep doing science & keep looking up!
