June 22, 2012
Despite claims in the 1890s that Mars was filled with canals teeming with water, research over the past several decades has suggested that in fact, Mars has only a tiny amount of water, mostly near its surface. Then, during the 1970s, as part of NASA’s Mariner space orbiter program, dry river beds and canyons on Mars were discovered—the first indications that surface water may have once existed there. The Viking program subsequently found enormous river valleys on the planet, and in 2003 it was announced that the Mars Odyssey spacecraft had actually detected minute quantities of liquid water on and just below the surface, which was later confirmed by the Phoenix lander.
Now, according to an article published yesterday in the journal Geology, there is evidence that Mars is home to vast reservoirs of water in its interior as well. The finding has weighty implications for our understanding of the geology of Mars, for hopes that the planet may have at some point in the past been home to extraterrestrial life and for the long-term prospects of human colonization there.
“There has been substantial evidence for the presence of liquid water at the Martian surface for some time,” said Erik Hauri, one of the study’s authors. “So it’s been puzzling why previous estimates for the planet’s interior have been so dry. This new research makes sense.”
The research team, led by led by University of New Mexico scientist Francis McCubbin, didn’t even have to go all the way to Mars to find the water—they just closely looked at a pair of meteorites we’ve already had for some time. The Shergotty meteorite, which crashed in Bihar, India in 1865, and the Queen Alexandria Range 94201 meteorite, which landed in Antarctica and was discovered in 1994, were both ejected from Mars roughly 2.5 million years ago. Because they formed due to volcanic activity, when molten Martian mantle was brought to the surface and crystallized, they can tell us a great deal about the planet’s insides.
“We analyzed two meteorites that had very different processing histories,” Hauri said. “One had undergone considerable mixing with other elements during its formation, while the other had not.” For both of the meteorites, the team looked specifically at the amount of water molecules locked inside crystals of the mineral apatite and used this as a proxy for how much water was contained in the original rock on Mars that produced the meteorites. To determine the precise amount of water, they used a technology called secondary ion mass spectrometry, which shoots a focused beam of ions at the sample and measures the amount of ions that bounce off of the surface.
The amount of water in the meteorites suggested that the Martian mantle contains somewhere between 70 and 300 parts per million of water—an amount strikingly similar to Earth’s own mantle. Because both the samples contained roughly the same water content despite their different geological histories on Mars, the researchers believe that the planet incorporated this water long ago, during the early stages of its formation. The paper also provides us with an answer for how underground water may have made its way to the Martian surface: volcanic activity.
Earlier this week, we discussed how solar radiation is among the many problems that face potential human colonization of Mars, but finding a huge underground store of water inside the planet would still go a long way towards making settlement a legitimate possibility. In the long-term, drilling for underground water may be cheaper and easier than, say, trying to melt surface ice, or subsisting off the tiny amount of surface water that we know is present.
Additionally, the finding is getting an entire separate crowd excited: those who are hoping to find fossil or other evidence that Mars once supported life. The fact that water has apparently existed on the planet for such a long time makes the odds of life originating there just a little less scant.
All this from a pair of meteorites that crashed on our planet over a century ago. Just imagine what we might learn during future missions to Mars, such as NASA’s unmanned space laboratory, Curiosity, which will land on Mars on August 5th.
Still, it won’t be easy. Watch this NASA video to learn about the riskiest part of the whole mission—the seven minutes between when the rover hits the top of the Martian atmosphere and when it touches down.
May 22, 2012
In 2007, new images of Mars wowed astronomers and the general public with something out of the pages of a sci-fi comic: extraterrestrial caves. Photos produced by orbiting satellites showed evidence of “skylights” into underground caverns, and thermal imaging indicating that these caves remained at a constant temperature day and night. In recent years, caves and related structures have also been discovered on our moon and on Jupiter’s moon Titan. The concept of extraterrestrial caves has plainly moved from fiction to reality, and scientists are eager to start exploring.
Why is the scientific world so excited about extraterrestrial caves? For many, they represent the next frontier in the search for extraterrestrial life. For others, they are our best bet for someday constructing and maintaining habitable colonies on other planets.
In October 2011, an interdisciplinary group of geologists, cave explorers, earth scientists, astrobiologists and other researchers met in New Mexico for the first time to discuss the science and implications of caves on other planets. Published earlier this month in the journal Eos, the results of the meeting give us a tantalizing hint of what discoveries may come during our lifetimes as space missions begin exploring these hidden crevices throughout the solar system.
Caves are a remarkably promising location to begin looking for life, the scientists report. Because they are isolated and protected from the surface, they can provide a diverse range of microenvironments—and the greater number of different habitats, the greater the chance life will happen to evolve in one of them. The study of caves here on earth has shown us that many unusual (and in some cases, downright bizarre) life forms can evolve in caves, and many of these result from the abundance of sulfur, metals and other chemicals that are likely to be available in caves on other planets as well.
The group of researchers also theorized about possible means of exploring caves on other planets and moons. Although images produced by satellites and other spacecraft can sometimes reveal the existence of caves, new technologies are clearly necessary to actually explore their interiors and extract samples that might contain life. Exploration and mapping could hypothetically be undertaken by either human or robotic means, although the latter seems more realistic at this point.
Ground-based exploration vehicles, such as the Mars rovers, could be equipped to enter and navigate caves, but the group noted that such devices would require better autonomous decision-making. Robotic explorers would need to be able to avoid hazards and make decisions about what data to collect without communicating with earth, since the cave walls and ceilings could block the transmission of radio signals.
The scientists even considered how caves can foster human exploration of other moons and planets. They might, for example, be good places to look for ice and other resources that would help groups of humans explore and perhaps even inhabit far-flung extraterrestrial bodies. They could also provide physical protection for colonies and experiments. Close study of caves on earth—their geologic context, the means by which they formed, the microenvironments they provide and other factors—will help us know what to expect in planning cave excursions elsewhere.
Although all of this cave talk sounds a bit like it belongs in a summer Hollywood blockbuster rather than the proceedings of an academic conference, consider this: Exploration of the ocean floor and the moon were both predicted in science fiction before being taken seriously by the scientific establishment. After technology caught up with the human imagination, these ideas didn’t seem so far-fetched.
It may take decades or longer, but it appears as though exploration of extraterrestrial caves is on the same track. What’s more uncertain, though, is what marvels we’ll find when we get there.