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 Stamenković, 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 Stamenković. 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, Stamenković, Fischer, and their colleagues Michael Mischna at JPL and Lewis Ward (MS ’14, PhD ’17) 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, Stamenković says.

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Materials provided by California Institute of Technology. Original written by Robert Perkins. Note: Content may be edited for style and length.

One of the twin MarCO CubeSats snapped this image of Mars on Oct. 3 — the first image of the Red Planet ever produced by this class of tiny, low-cost spacecraft. The two CubeSats are officially called MarCO-A and MarCO-B but nicknamed “EVE” and “Wall-E” by their engineering team.

A wide-angle camera on top of MarCO-B produced the image as a test of exposure settings. The MarCO mission, led by NASA’s Jet Propulsion Laboratory in Pasadena, California, hopes to produce more images as the CubeSats approach Mars ahead of Nov. 26. That’s when they’ll demonstrate their communications capabilities while NASA’s InSight spacecraft attempts to land on the Red Planet. (The InSight mission won’t rely on them, however; NASA’s Mars orbiters will be relaying the spacecraft’s data back to Earth.)

This image was taken from a distance of roughly 8 million miles (12.8 million kilometers) from Mars. The MarCOs are “chasing” Mars, which is a moving target as it orbits the Sun. In order to be in place for InSight’s landing, the CubeSats have to travel roughly 53 million miles (85 million kilometers). They have already traveled 248 million miles (399 million kilometers).

MarCO-B’s wide-angle camera looks straight out from the deck of the CubeSat. Parts related to the spacecraft’s high-gain antenna are visible on either side of the image. Mars appears as a small red dot at the right of the image.

To take the image, the MarCO team had to program the CubeSat to rotate in space so that the deck of its boxy “body” was pointing at Mars. After several test images, they were excited to see that clear, red pinprick.

“We’ve been waiting six months to get to Mars,” said Cody Colley, MarCO’s mission manager at JPL. “The cruise phase of the mission is always difficult, so you take all the small wins when they come. Finally seeing the planet is definitely a big win for the team.”

For more information about MarCO, visit: https://www.jpl.nasa.gov/cubesat/missions/marco.php

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Materials provided by NASA/Jet Propulsion Laboratory. Note: Content may be edited for style and length.

Black widow spiders and their relatives, native to temperate climates in North America, Europe, Asia, Australia, Africa and South America, produce an array of silks with exceptional materials properties.

Scientists have long known the primary sequence of amino acids that make up some spider silk proteins and understood the structure of the fibers and webs. Previous research theorized that spider silk proteins await the spinning process as nano-size amphiphilic spherical micelles (clusters of water soluble and non-soluble molecules) before being funneled through the spider’s spinning apparatus to form silk fibers. However, when scientists attempted to replicate this process, they were unable to create synthetic materials with the strengths and properties of native spider silk fibers.

“The knowledge gap was literally in the middle,” Northwestern’s Nathan C. Gianneschi said. “What we didn’t understand completely is what goes on at the nanoscale in the silk glands or the spinning duct — the storage, transformation and transportation process involved in proteins becoming fibers.”

Gianneschi is the Jacob and Rosaline Cohn Professor in the department of chemistry in the Weinberg College of Arts and Sciences and in the departments of materials science and engineering and of biomedical engineering in the McCormick School of Engineering. He and Gregory P. Holland, associate professor in the department of chemistry and biochemistry at SDSU and the author of more than 40 papers on spider silk, are the paper’s co-corresponding authors.

The research will be published online the week of Oct. 22 in the Proceedings of the National Academy of Sciences (PNAS).

Utilizing complementary, state-of-the-art techniques — nuclear magnetic resonance (NMR) spectroscopy, the same technology utilized in MRI, at SDSU, followed by electron microscopy at Northwestern — the research team was able to more closely see inside the protein gland where the silk fibers originate, revealing a much more complex, hierarchical protein assembly.

This “modified micelles theory” concludes that spider silk proteins do not start out as simple spherical micelles, as previously thought, but instead as complex, compound micelles. This unique structure is potentially required to create the black widow spider’s impressive fibers.

“We now know that black widow spider silks are spun from hierarchical nano-assemblies (200 to 500 nanometers in diameter) of proteins stored in the spider’s abdomen, rather than from a random solution of individual proteins or from simple spherical particles,” Holland said.

If duplicated, “the practical applications for a material like this are essentially limitless,” Holland said, and could include high-performance textiles for military, first responders and athletes; building materials for cable bridges and other construction; environmentally friendly replacements for plastics; and biomedical applications.

“One cannot overstate the potential impact on materials and engineering if we can synthetically replicate this natural process to produce artificial fibers at scale,” said Gianneschi, who also is the associate director of the International Institute for Nanotechnology and a member of the Simpson Querrey Institute and the Chemistry of Life Processes Institute at Northwestern. “Simply put, it would be transformative.”

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Materials provided by Northwestern University. Note: Content may be edited for style and length.