EARTH
A Martian outcrop contains a mineral indicating that a past environment was wet and non-acidic, possibly favorable to life. PHOTO/NASAJPL-Caltech/Cornell University
Even 15 years after the release of “Good Will Hunting,” there remains something appealing about watching the title character, a mathematically inclined janitor at MIT, scribble the solution to an unsolved mathematics problem on a hallway blackboard. In reality, there are a number of unsolved problems in mathematics, seven of which were designated in 2000 by the Clay Mathematics Institute as “Millennium Prize Problems,” each with a purse of $1,000,000. To date, only one has been solved.
Earth science, too, has put forth a long stream of unsolved questions. In fact, solving one question typically floods the field with new lines of investigation. The discovery, for example, in the mid-19th century that carbon dioxide traps heat in Earth’s atmosphere led scientists to engage in lengthy studies — many that continue today — on the mechanics of the greenhouse effect, emission sources and impacts on global climate.
So, what are today’s biggest unanswered questions in earth science? EARTH Associate Editor Kathryn Hansen posed this question to experts across a variety of earth science disciplines, from atmospheric and space science to glaciology. The experts weighed in with their favorite questions and discussions of the questions’ history and relevance, along with the current approaches to finding the answers.
Read on for paraphrased versions of the experts’ responses. There’s no million-dollar prize on the line, but if you’re up for the challenge, grab a pencil or laptop and get ready to think. You never know how or where the next paradigm-changing solution will arise.
3. Is there life on any other planetary body in our solar system?
by Alfred McEwen, planetary geologist, Arizona State University
NASA and others have been trying to address this question for decades, but it’s very difficult. Some scientists think that sample return is the only way to get a definitive result, although it might require several attempts to get the right samples and it is very expensive (about $10 billion for Mars). And even positive results might still be controversial. In-situ analysis is a less expensive approach, but still on the order of $1 billion to $2 billion per mission, and results would likely be controversial.
Maybe we’ll get lucky and find credible evidence in a Martian meteorite, but then the possibility of terrestrial contamination is very difficult to rule out. It was previously announced that signs of life were found in a Martian meteorite, but the strong consensus of the scientific community is now against this conclusion.
Icy moons in the outer solar system, such as Saturn’s Enceladus, could harbor life, but we know much less about these worlds than about Mars and need more basic robotic exploration. The outer solar system is even more expensive to explore than is Mars.
The good news is that efforts to find life result in new knowledge about the physical and chemical processes and geologic history of these interesting worlds. For example, the Viking Orbiters (which carried the Mars landers to search for life in the 1970s) revolutionized our understanding of Mars’ global geology, soil and atmosphere. Comparison of the atmospheric composition to gases trapped in some meteorites led to recognition that these rocks came from Mars, which in turn led to many more new results.
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