Exploring oceans on other planets, such as the one underneath the ice crust of Europa, gets at one of science’s most profound questions: how unique is the planet we live on?
Exoplanetary oceans, like those possibly harbored by planets in the Gliese 581 system in this artist’s conception, could provide valuable information on just how unusual Earth is. Image Credit: NASA.gov
The budget appropriations for NASA for the 2016 fiscal year look to invigorate the exploration of outer space, in particular exoplanetary oceans. The Fiscal Year 2016 Commerce, Justice, and Science Appropriations bills from the House and the Senate increase NASA’s planetary science budget by 8.3 and 8.1 percent, respectively. In particular, both call for increased funding for a mission to Europa, a moon of Jupiter.
According to Jim Garvin, the Sciences and Exploration Directorate chief scientist at NASA’s Goddard Space Flight Center, NASA has been exploring the idea of sending a mission to Europa ever since the Galileo mission found evidence of ice on Europa’s surface in 1997. Since then, NASA has studied almost 20 different mission concepts as scientists have tried to get a better understanding of what challenges a mission might face.
With the new 2016 budget as written, a Europa mission in some form has gotten the full green light. The House approved $140 million for Europa, $110 million more than the $30 million originally requested by the White House. The extra funds seek to finally kick-start the Europa mission.
An artist’s rendering of the proposed mission to Europa. Image Credit: Jet Propulsion Labratory
As currently proposed, the satellite would perform 45 flybys of Europa, imaging the surface as it passes over. Jupiter’s high level of radiation necessitates this method.
This may be just the first in a series of planetary exploration missions. The House bill also sets aside $86 million for the creation of an “Ocean Worlds Exploration Program…whose primary goal is to discover extant life on another world.” The program would be set up to further exploration of other worlds bearing oceans, such as Saturn’s moons of Titan, which has oceans of methane, and Enceladus, which has water-rich plumes.
However, some argue there is another frontier that should be receiving this kind of attention: the Earth’s ocean. In a 2014 paper in the Smithsonian Magazine, Robert Ballard, the oceanographer and explorer known for discovering the Titanic wreck, expressed dismay that “we know less about 71 percent of the Earth’s landscape than about the far side of the moon.” In a TED talk in 2008, Ballard highlighted how we only explored the Mid-Ocean ridge, which covers 23 percent of the Earth’s surface, after Apollo 11.
Even John Steinbeck, in a letter to Popular Science in 1969, lamented the lack of interest in studying Earth’s oceans: how humans “peck like sandpipers along the edges” of the ocean without investigating further, and how we are “incurable, incorrigible romantics” infatuated with the idea of exploring space.
Both Steinbeck and Ballard argue that exploring Earth’s oceans can provide immediate, quantifiable returns. As an example, Ballard notes more than half of the U.S. lies under the sea, and in this U.S.-exclusive economic zone are potentially trillions of dollars of oil and natural gas. “I believe in just enriching the economy,” says Ballard.
The discussion of ocean and space exploration is inevitably rooted in economics. An economy of finite resources creates a system of prioritization, and Ballard, knowing the importance of Earth’s oceans, wants to make ocean exploration a higher priority. For comparison, in 2015, NASA’s space exploration budget was $4.4 billion, and the National Oceanic and Atmospheric Administration’s ocean exploration budget was $28 million.
However, this system of priorities supports the notion that areas of science or exploration can be discretized, which can be a harmful way to view science, says Chris McKay, an astrobiologist at NASA’s Ames Research Center. “Science isn’t as compartmentalized as, inevitably, the political process would suggest,” he says.
What is important to remember, argues McKay, is that exploring our own oceans and exploring oceans on other planets both contributes to our understanding of how unique a planet Earth is, and how unlikely our existence is in the universe.
“If you approach this scientifically, there’s no conflict,” says McKay. “… Scientific inquiry … goes wherever the data and curiosity takes it and has no fences or walls.”
McKay has made a career out of exploring the Earth and Earth-like places on other planets. For example, he likens the cold of Antarctica, where his research is currently focused, to the unexplored surface of Europa; deserts such as the Mojave, Atacama, and Namib to Mars; and conditions thousands of feet below our own oceans to the oceans of Enceladus.
The great similarity of these cold, dry, or deep ocean locations on other planets to locations on Earth, combined with the disparity in how much life they exhibit, gives one a great sense of perspective on how unusual our home is, he said.
“Studying other planets, I have to admit, has heightened my appreciation of Earth,” McKay said. “As a kid I took it for granted … (but) then you spend decades studying other worlds where there’s no biology at all, and you’re scratching and digging and looking for any little bit of life, you realize ‘Wow, Earth is really full of it; it’s rich.’ And that’s good.”
This appreciation isn’t limited to astrobiologists. John Mather, an astrophysicist at NASA’s Goddard Space Flight Center, won a Nobel Prize for his work with the Cosmic Background Explorer (COBE), which analyzed fluctuations in the cosmic microwave background and is credited with ushering in the era of “precision cosmology.” According to Mather, work like that done by COBE (to be followed in 2018 by the James Webb Space Telescope (JWST)) can also help us understand Earth’s stature in the universe.
“Precision cosmology is just the beginning of the history of how we got here,” says Mather. “If we could understand the Big Bang (which the COBE data provided strong evidence for) … we would understand the origin of the solar system and the chemical composition of the solar system. We would understand more about whether Earth is unusual … we could begin to understand whether we’re unusual in the universe.”
McKay sees the similarities between what Mather studies and his own studies. “In a sense (cosmology) provides a context: Are there lots of Earths or are there not? And in fact astrobiology is trying to do the same thing biologically.”
These two different fields can be seen in alliance with one another. They study other planets, and the universe, and yet they both provide valuable insight into what makes the Earth special. “I study the Earth. I study other planets,” McKay says. “I have no choice but to do both.”
Studying Earth’s oceans is vital in order to understand the uniqueness of our planet, and so is studying other planets, because both inform us about the Earth, says McKay. “The connection to Earth is a necessary one,” he argues, regardless of the field of science. That connection provides context, and is what makes the exploration of any frontier so exciting.
Alec Drobac is a senior physics major at Middlebury College in Vermont. He hopes to pursue a career as a theoretical physicist, potentially in the field of astrophysics or cosmology. Originally from California, he is particularly concerned with water usage and conservation, as well as the advancement of technology in agriculture.