By Liz Lewis ’22
Managing Editor of Content
Professor M. Darby Dyar never intended to be a planetary geologist — or a scientist at all, for that matter. As an undergraduate at Wellesley College, she majored in art history and geology, determined to build a career as a journalist. However, encouraged by the few female mentors in STEM she encountered, she set herself on a path that would grow into a renowned career in planetary science. Now, as a decorated researcher and the chair of Mount Holyoke’s astronomy department, Dyar adds another accolade to her name: deputy principal investigator for Venus Emissivity, Radio Science, InSAR, Topography & Spectroscopy, or VERITAS for short, one of two missions to Venus recently approved for NASA’s Discovery Program.
“I’ve spent hundreds of hours on Venus proposals,” Dyar said. “To say that I’m overjoyed with this is an understatement.”
VERITAS and its sister program, Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging, Plus, also known as DAVINCI+, will be the first missions to Venus in over 30 years. Both aim to advance scientific knowledge about the under-explored planet’s atmosphere and surface. VERITAS will operate with a focus on mapping Venus’ surface and geological history, while DAVINCI+ will send instruments into the planet’s atmosphere to investigate its chemical makeup. As deputy principal investigator, Dyar said she will act as the “number two scientist” on the mission. “If anything should happen to the lead scientist, I have to step into her shoes,” she said. “The mission has two different instruments. One of them does … topography of the surface and uses a radar, and the other instrument is a spectrometer. I do spectroscopy, so that’s sort of my baby.” Dyar has been developing the spectrometer with scientists in Berlin for about five years, and will continue to do so until its launch in 2027.
The twin missions’ approval is a massive victory for Dyar, her peers and the scientific community at large. “The Venus community has waited decades for this moment, and to have NASA give us two missions in one, both complementary, is out of this world,” Dyar told NPR in a recent article and radio segment.
Today, Venus is anything but habitable, with an atmosphere thick with carbon dioxide and surface temperatures reaching 864 degrees Fahrenheit. Dyar maintains there is more to the planet than meets the eye. “Venus fools you, because right now it’s this hot, high pressure, ugly place covered with basalt,” she said. “But … everything that came before that is almost erased by those lavas.” Scientists speculate that in its early history, Venus’ climate may have been strikingly similar to Earth’s, potentially complete with distinct land masses and shallow oceans. It also may have reached its current form as a result of the same greenhouse effect threatening Earth today.
According to Dyar, Earth’s secret to habitability is its oceans, which store the CO2 that would otherwise escape into the atmosphere and create a toxic, uninhabitable environment.
“Earth has geological processes that end up forming CO2-bearing minerals in the ocean, and that’s what saves Earth, is that we don’t have CO2 in the atmosphere,” Dyar explained. “So imagine that Venus was once like that. Venus is closer to the sun and the sun heats up over time, so there came a point where liquid water was no longer stable on Venus, and so all the CO2 that had been dissolved in the oceans on Venus now suddenly had to go into the atmosphere.”
Dyar explained that, as solar winds can easily break bonds between hydrogen and oxygen, the remaining water vapor in Venus’ atmosphere boiled off. As a result, Venus is now a “runaway greenhouse,” which explains its high surface temperature and pressure levels. “The pressure on Venus is equivalent to the bottom of the ocean in some places,” Dyar said. “And it’s all because of, … effectively, global warming having run away on Venus.” By looking at Venus, scientists may be able to form a better understanding of how planets like Earth age. “I mean, it’s not gonna happen on Earth for a billion years,” Dyar clarified. “But there are aspects of this process that will inform our understanding of global warming on Earth, which is really important, too.”
Planetary scientists vying for NASA’s resources are frequently split between Earth’s next-door neighbors — Venus and Mars. In recent decades, Venus has consistently gotten the short end of the stick in favor of the red planet. These two sister missions will be the first trips to Venus in over three decades. To Dyar, this is long overdue. “There’s a huge knowledge gap in our solar system,” she said. “We haven’t been to Venus in more than 30 years, so for that reason alone, it’s become really critical to fill in the gap.”
“It’s politics, pure and simple,” Dyar said, explaining the attention and resource discrepancy between the two planets. “NASA has three different ways of choosing missions. One of them is called a flagship mission which is basically [when] headquarters or Congress decides that something is an important target, and they just do it.” The Mars Rovers, Mars 2020 and Mars Science Laboratory were all flagship missions, which fall under NASA’s Solar System Exploration program. According to Dyar, the other two main classes of planetary missions are the Discovery and New Frontiers programs, which handle small and mid-size missions, respectively. These, unlike the mandated flagship missions, serve as competition ground for scientists, who submit proposals to NASA headquarters for approval.
“My feeling is there’s just been so much emphasis on Mars, and looking for water on Mars, that Venus, I think, has probably suffered by comparison,” Dyar said. “The other kinds of missions that we’ve been sending to asteroids or the outer planets, those don’t suffer so much [from] comparison to Mars. It’s not for lack of good proposals, I can tell you that.”
A lot of the emphasis on Mars comes back to the enduring question of whether life has ever existed in the solar system beyond Earth. In 1996, a Martian rock fell to Earth as a meteorite appearing to contain fossils of a bacteria-like life form scientists speculated had Martian origin. Though investigators eventually found these abnormalities to be inorganic, the meteorite made worldwide headlines and, according to Dyar, spurred much of the scientific community’s fixation on Mars. “It kind of lit a fire under the Mars program, and that’s what started this current progression of Mars missions, was the idea that there might be life on Mars,” Dyar said. “There are rocks on Mars that also formed in the presence of water, but we now know that Mars only had water for about 300 million years, and that’s not enough to … get life going.”
Venus, however, likely had water on its surface for two to three billion years, making it potentially habitable for a large portion of its history. “Three billion years is a long time for life [to develop],” Dyar said. “If, indeed, the processes that cause life to emerge are universal, then three billion years ought to be long enough for it to have happened on Venus.”
Over the past three decades, as Mars received both attention and funding from NASA, Venus has gone unexplored. Now, with the resources of two missions newly at their disposal, planetary scientists who study Venus have a lot to look forward to. According to Dyar, Venus is remarkably Earth-like beneath its toxic atmosphere, its landscape potentially featuring familiar formations such as volcanoes and continents.
“I'm excited about the possibility that we might detect active volcanism on Venus,” Dyar said. “When a volcano erupts, … there’s a lot of gas that dissolves in the magma at depth. When it comes to the surface, the gas all escapes, and so from the orbit, you can see the gas signature and detect the volcanism.” Dyar is also responsible for designing a new spectrometer that will help distinguish the basalt that covers most of Venus from other types of rocks, which may be remnants of old Earth-like continents. “If there’s continents, there was probably plate tectonics,” Dyar continued. “And if there’s plate tectonics, plate tectonics and water are all tied up together, so it means that Venus was once way more Earth-like than people give it credit for, which is really neat.”
VERITAS will likely be the capstone to Dyar’s career in planetary geology — as she put it, she’s “going out with a bang.”
Before settling into an intellectual home at Mount Holyoke, she taught geology at the University of Oregon. Throughout her years in the field, she has been awarded over $10 million in grants from NASA and the National Science Foundation and has been published in over 260 scientific papers. As for her inspirations, she credits the female role models she’s encountered in the scientific field — from a high school science teacher to her professional peers.
Dyar’s decades-long career as a woman in STEM has not come without challenges. She has faced harassment, been denied opportunities based on her gender and has grown used to being the only woman in the rooms where decisions are made.
“My mother used to say that if women don’t help other women, no one else will,” Dyar said. “Certainly that was true in her time and in my time, because one of the reasons I had so much trouble was there were no women ahead of me to make my life easier.”
Dyar urged young women in her field to “take seriously the fact that you’re going to be a role model, whether you want to be or not.” This sentiment, which Dyar punctuated with a dry laugh, comes from years of serving in that role simply by virtue of her gender. “At every stage of my career, I’ve been scrutinized by the people behind me,” she said.
But Dyar isn’t bitter about this reality — to her, being a role model is the most important part of the job, and of her career as a whole.
“There's nothing as important as mentoring the next generation,” she said. “I’ve gotten a lot of awards for my research which I’m really proud of, but at the end of the day, I’m not going to be lying on my deathbed thinking about the papers I wrote, I’m gonna be thinking about all of the people whose lives I changed by being an advisor or a mentor or even just a professor.” She continued, “I have a whole scrapbook full of letters from Mount Holyoke students that say, ‘you changed my life, Darby,’ and ‘I’ll never forget you,’ and, you know, there’s just nothing more important than that.”