A team led by scientists at Caltech and the Jet Propulsion Laboratory (JPL), which Caltech manages for NASA, has calculated that if liquid water exists on Mars, it could—under specific conditions—contain more oxygen than previously thought possible. According to the model, the levels could even theoretically exceed the threshold needed to support simple aerobic life.
That finding runs contrary to the current, accepted view of Mars and its potential for hosting habitable environments. The existence of liquid water on Mars is not a given. Even if it is there, researchers have long dismissed the idea that it might be oxygenated, given that Mars’s atmosphere is about 160 times thinner than that of Earth and is mostly carbon dioxide.
“Oxygen is a key ingredient when determining the habitability of an environment, but it is relatively scarce on Mars,” says Woody Fischer, professor of geobiology at Caltech and a co-author of a Nature Geoscience paper on the findings, which were published on October 22.
“Nobody ever thought that the concentrations of dissolved oxygen needed for aerobic respiration could theoretically exist on Mars,” adds JPL’s Vlada Stamenkovic, lead author of the Nature Geoscience paper.
Finding liquid water on Mars is one of the major goals of NASA’s Mars program. In recent months, data from a European spacecraft have suggested that liquid water may lie beneath a layer of ice at Mars’s south pole. It has also been hypothesized that water could exist in salty subsurface pools, because perchlorate salts (compounds of chlorine and oxygen) have been detected at various places on Mars. Salt lowers the freezing point of water, which means that water with perchlorate in it could potentially stay liquid despite the freezing temperatures on Mars, where summer nights on the equator can still dip down to -100 degrees Fahrenheit.
That hypothetical salty water is what interested Fischer and Stamenkovic. Oxygen enters water from the atmosphere, diffusing into the liquid to maintain an equilibrium between the water and the air. If salty water were close enough to the surface of the Martian soil, then it could effectively absorb oxygen from the thin atmosphere.
To find out just how much oxygen could be absorbed, Stamenkovic, Fischer, and their colleagues Michael Mischna at JPL and Lewis Ward at Harvard, did two things: First, they developed a chemical model describing how oxygen dissolves in salty water at temperatures below the freezing point of water. Second, they examined the global climate of Mars and how it has changed over the past 20 million years, during which time the tilt of the axis of the planet shifted, altering regional climates. The solubility and climate models together allowed the researchers to infer which regions on Mars are most capable of sustaining high oxygen solubilities, both today and in the planet’s geologically recent past.
The team found that, at low-enough elevations (where the atmosphere is thickest) and at low-enough temperatures (where gases like oxygen have an easier time staying in a liquid solution), an unexpectedly high amount of oxygen could exist in the water—a value several orders of magnitude above the threshold needed for aerobic respiration in Earth’s oceans today. Further, the locations of those regions have shifted as the tilt of Mars’s axis has changed over the past 20 million years. During that time, the highest oxygen solubilities have occurred within the past five million years.
The findings could inform future missions to Mars by providing better targets to rovers searching for signs of past or present habitable environments, Stamenkovic says.
Their paper is titled “O2 solubility in Martian near-surface environments and implications for aerobic life.”
By Robert Perkins
Native American Trade Far Greater than Once Thought
A research team including Matthew Sanger, assistant professor of anthropology at Binghamton University, State University at New York, has found a copper band that indicates ancient Native Americans engaged in extensive trade networks spanning far greater distances than what has been previously thought.
“Our research shows that Native Americans living roughly 3,500 years ago were engaged in extensive trade networks spanning far greater distances than we had previously assumed (more than 1,500 km) and across various regions that we did not know were connected (the Great Lakes and the coastal Southeast),” said Sanger. “While we still struggle to understand the nature of these trade networks, our findings suggest that they moved not only objects (such as the piece of worked copper we recovered) but may also be a pipeline through which belief systems, cultural values, and societal norms were also exchanged. The possibility that information also traveled along trade networks is evidenced by the shared use of cremation found alongside the exchange of copper between the two regions.”
Sanger and colleagues found a copper band, slightly wider than a bracelet, alongside the cremated remains of at least seven individuals at a burial site in coastal Georgia. Prior to their discovery, both copper and cremated human remains dating to the Archaic period (around 3,000–8,000 years ago) were rarely, if ever, found in the Southeast United States. The copper band and burials were located in the center of a Late Archaic shell ring—circular deposits thought to have been used by Native Americans as both residential sites and as places of ritual gatherings and feasting events. Radiometric dating using an accelerated mass spectrometer indicate that the remains and band are both more than 3,500 years old. This is significant, as it pushes the practice of cremation, as well as the use of copper, in the region more than a millennium older than previously thought.
Remarkably, the copper band was not manufactured from local materials but, rather originated in the Great Lakes region, more than 1,500 km away. Copper sources each have their own unique chemical makeup, including very small amounts of trace elements. As such, archaeologists can match manufactured objects to their sources by comparing their chemical signatures, or “fingerprints.” Using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS), researchers at Ball State, the Field Museum, and the New Jersey State Museum determined the chemical makeup of the copper band was most similar to sources found near the Great Lakes. While archaeologists had long known copper was exchanged out of the Great Lakes region, the discovery made by Sanger and his colleagues extended previously documented boundaries of Archaic Period copper exchange by nearly 1,000 km.
The use of cremation is also notable, as this practice was virtually absent in the Southeast United States during the Archaic period, yet quite common further to the north, including in the Great Lakes, where the copper originated. The co-occurrence of copper use and cremation practices suggests, according to Sanger and colleagues, that these two regions were more closely linked than previously assumed. The possibility that the two regions shared cosmological worldviews or religious practices would suggest direct connections across huge amounts of space.
According to the authors, these findings lend insight on emergent patterns of hierarchical social organization in the Archaic Southeast United States.
“Defining social complexity is always difficult—but our research shows that people were organized to a degree that allowed the formation of vast trade networks spanning half of a continent more than 3,000 years ago,” said Sanger. “Considering that these trade networks likely moved both information and objects, we argue that they were not simple “down the line” exchanges—meaning that objects would slowly move between people over large amounts of time, perhaps through trade between friends and neighbors or as inherited items when someone died. Rather, the movement of information across more than 1,500 km suggests that exchange networks were more formal and direct. Such formal and direct trade networks suggest sustained relations between diverse communities, which must have been sustained by relatively complex social institutions. We assume these social institutions were religious or ritual in nature considering that we are looking at a multiple-person cremation in the center of a circular deposit of food remains.”
Science & Technology, Harpur
How Can Driverless Vehicles Make Good Moral Choices?
A massive new survey developed by MIT researchers reveals some distinct global preferences concerning the ethics of autonomous vehicles, as well as some regional variations in those preferences.
The survey has global reach and a unique scale, with over 2 million online participants from over 200 countries weighing in on versions of a classic ethical conundrum, the “Trolley Problem.” The problem involves scenarios in which an accident involving a vehicle is imminent, and the vehicle must opt for one of two potentially fatal options. In the case of driverless cars, that might mean swerving toward a couple of people, rather than a large group of bystanders.
“The study is basically trying to understand the kinds of moral decisions that driverless cars might have to resort to,” says Edmond Awad, a postdoc at the MIT Media Lab and lead author of a new paper outlining the results of the project. “We don’t know yet how they should do that.” Still, Awad adds, “We found that there are three elements that people seem to approve of the most.”
Indeed, the most emphatic global preferences in the survey are for sparing the lives of humans over the lives of other animals; sparing the lives of many people rather than a few; and preserving the lives of the young, rather than older people.
“The main preferences were to some degree universally agreed upon,” Awad notes. “But the degree to which they agree with this or not varies among different groups or countries.” For instance, the researchers found a less pronounced tendency to favor younger people, rather than the elderly, in what they defined as an “eastern” cluster of countries, including many in Asia.
The paper, “The Moral Machine Experiment,” was published in October in Nature. The authors include Awad, Sohan Dsouza, and Iyad Rahwan, Associate Professor of Media Arts and Sciences at MIT Institute for Data, Systems, and Society.
To conduct the survey, the researchers designed what they call “Moral Machine,” a multilingual online game in which participants could state their preferences concerning a series of dilemmas that autonomous vehicles might face. For instance: If it comes right down it, should autonomous vehicles spare the lives of law-abiding bystanders, or, alternately, law-breaking pedestrians who might be jaywalking? (Most people in the survey opted for the former.)
All told, “Moral Machine” compiled nearly 40 million individual decisions from respondents in 233 countries; the survey collected 100 or more responses from 130 countries. The researchers analyzed the data as a whole, while also breaking participants into subgroups defined by age, education, gender, income, and political and religious views. There were 491,921 respondents who offered demographic data.
The scholars did not find marked differences in moral preferences based on these demographic characteristics, but they did find larger “clusters” of moral preferences based on cultural and geographic affiliations. They defined “western,” “eastern,” and “southern” clusters of countries, and found some more pronounced variations along these lines. For instance: Respondents in southern countries had a relatively stronger tendency to favor sparing young people rather than the elderly, especially compared to the eastern cluster.
Awad suggests that acknowledgement of these types of preferences should be a basic part of informing public-sphere discussion of these issues. In all regions, since there is a moderate preference for sparing law-abiding bystanders rather than jaywalkers, knowing these preferences could, in theory, inform the way software is written to control autonomous vehicles.
Peter Dizikes, Massachusetts Institute of Technology Press Office