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Astronomy
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There are Important Differences Between the Ice Caps on Mars
In the 17th century, astronomers Giovanni Domenica Cassini and Christian Huygens noted the presence of hazy white caps while studying the Martian polar regions. These findings confirmed that Mars had ice caps in both polar regions, similar to Earth. By the 18th century, astronomers began to notice how the size of these poles varied depending on where Mars was in its orbital cycle. Along with discovering that Mars’ axis was tilted like Earth’s, astronomers realized that Mars’ polar ice caps underwent seasonal changes, much like Earth’s.
While scientists have been aware that Mars’ polar ice caps change with the seasons, it has only been within the last 50 years that they have realized that they are largely composed of frozen carbon dioxide (aka. “dry ice”) that cycles in and out of the atmosphere – and questions as to how this happens remain. In a recent study, a team of researchers led by the Planetary Science Institute (PSI) synthesized decades of research with more recent observations of the poles. From this, they determined how the Martian poles differ in terms of their seasonal accumulation and release of atmospheric carbon dioxide.
The team was led by Dr. Candice Hansen, a Senior Scientist with the Planetary Science Institute (PSI) and a member of the HiRISE imaging team. She was joined by researchers from the Lunar and Planetary Laboratory (LPL) at the University of Arizona, the University of Nevada, the U.S. Geological Survey’s Astrogeology Science Center (USG-ASC), the Laboratory for Atmospheric and Space Physics at UC Boulder, IUCLA, the Astrophysics Research Centre at Queen’s University Belfast, the German Aerospace Center (DLR), and NASA’s Jet Propulsion Laboratory. The paper that details their findings recently appeared in the journal Icarus.
Mars’ south polar ice cap imaged by the HRSC camera on the ESA’s Mars Express. Credit: ESA/DLR/FU BerlinFor their study, Hansen and her colleagues relied on data acquired by Mars orbiters over the past few decades. They then compared this with more recent data from the High-Resolution Imaging Experiment (HiRISE) instrument on the Mars Reconnaissance Orbiter (MRO). This allowed them to track the growth and recession of the Martian ice caps, which cycle about a quarter of the planet’s atmosphere throughout a Martian year. The ultimate purpose was to learn more about the processes that shape the planet’s surface and overall environment. As Hansen summarized in a PSI press release:
“Everybody knows there’s a difference in how carbon dioxide interacts with the poles, but how many people understand why? That was what I was setting out to describe. And fortunately, I have a whole bunch of really talented co-authors who were willing to fill in their own pieces.”
Like Earth, Mars experiences seasonal changes due to its axial tilt, about 25 degrees relative to the orbital plane, compared to Earth’s tilt of about 23.5 degrees. But since Mars has a much longer orbital period (~687 days), the seasons last about twice as long as they do here on Earth. In addition, Mars has a greater orbital eccentricity – about 9% compared to 1.7% – which means its orbit is more elliptical. Because of this, Mars is farthest from the Sun when its northern hemisphere experiences Spring and Summer, while the south experiences Fall and Winter.
This means that summer in the southern hemisphere is shorter (while winter is longer in the north), coinciding with the dust storm season. As a result, the northern polar seasonal cap contains a higher concentration of dust than the south polar cap. “So ultimately, southern fall and winter bring the most freezing and lowest atmospheric pressure since so much of the atmosphere is frozen as dry ice,” said Hansen. “These are the major drivers of differences in seasonal behavior of carbon dioxide between the hemispheres. They’re not symmetric seasons.”
Mars’ Barchan Dunes, captured by the MRO’s HiRISE Camera. Credit: NASA/ HiRISE/MRO/LPL (UofA)There are also significant differences in terms of elevation between the northern and southern hemispheres—i.e., the Northern Lowlands and Southern Highlands. Differences between the northern and southern polar terrain also influence seasonal change. For example, black dust fans are distributed across the southern landscape, resulting from dry ice sublimating and causing dust plumes. As Hansen explained:
“A layer of carbon dioxide ice builds in the southern hemisphere fall, and over the course of the winter, it thickens and it becomes translucent. Then in the spring, the sun comes up, and light penetrates this ice layer to the bottom enough that it warms up the ground underneath. Now, gas is trapped under pressure. It’s going to look for any weak spot in the ice and rupture like a champagne cork.”
Once the gas finds a weak spot and ruptures the ice, it blows dark plumes of dust into the atmosphere. The dust is blown in different directions depending on the wind direction and lands in fan-shaped deposits. This process shapes the landscape by creating gully channels, colloquially called “spiders” (araneiforms) because of their arachnid-like appearance. While the northern hemisphere also experiences dust plums in the Spring, the relatively flat terrain causes them to form dune-like features. Said Hansen:
“When the Sun comes up and begins to sublimate the bottom of the ice layer, there are three weak spots – one at the crest of the dune, one at the bottom of the dune where it meets the surface and then the ice itself can crack along the slope. No araneiform terrain has been detected in the north because although shallow furrows develop, the wind smooths the sand on the dunes.”
These findings demonstrate that Mars is an active place, not only over the course of eons but on a seasonal and even daily basis.
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Archaeological Methods Reveal How Astronauts Work on the International Space Station
Archaeology is the study of human prehistory, so it seems incongruous to use its methods to study how humans behave in space. But that’s what astronauts aboard the International Space Station are doing.
When the ISS was designed, it was built around specific tasks and needs. Living areas like latrines, exercise spaces, and food preparation and eating spaces are designed to make the space station an effective and agreeable place to work and live. But it’s impossible to get these things right in any kind of facility. The people who end up working and living on the ISS find their own ways to use the spaces, which might not align with the intended purpose.
In an effort to understand how astronauts really use the spaces on the ISS, astronauts adapted methods used in archaeology. A team led by Justin Walsh of Chapman University in California had astronauts on the ISS take daily photos to see how different areas on the station are really used. They published their results in research titled “Archaeology in space: The Sampling Quadrangle Assemblages Research Experiment (SQuARE) on the International Space Station. Report 1: Squares 03 and 05” in the journal PLOS One.
SQuARE is part of the International Space Station Archaeological Project (ISSAP.)
“ISSAP aims to fill a gap in social science investigation into the human experience of long-duration spaceflight. As the largest, most intensively inhabited space station to date, with over 270 visitors from 23 countries during more than 23 years of continuous habitation, the International Space Station (ISS) is the ideal example of a new kind of spacefaring community—”a micro-society in a mini-world,” the authors explain.
“Our primary goal is to identify how humans adapt to life in a new environment for which our species has not evolved, one characterized by isolation, confinement, and especially microgravity,” the researchers write. The microgravity is especially interesting. Its benefits are the ability to work and move in 360 degrees and to do experiments that are impossible on Earth. The downside is that anything unrestrained simply floats away.
According to the authors, this is the first time archaeological fieldwork has been used in space. SQuARE had four goals:
- To develop a new understanding of how humans adapt to life in an environmental context for which we are not evolutionarily adapted, using evidence from the observation of material culture;
- To identify disjunctions between planned and actual usage of facilities on a space station;
- To develop and test techniques that enable archaeological research at a distance; and
- To demonstrate the relevance of social science methods and perspectives for improving life in space.
SQuARE adapted a method archaeologists use to study archaeological sites called the shovel test pit. Shovel test pits are shallow pits excavated in a grid overlain a site to see what artifacts might be underground. They’re used in the first phase of an archaeological study and help scientists determine where to dig deeper in subsequent phases.
Obviously, nobody’s digging actual holes into the space station. Instead of holes, the ISS crew took pictures of six locations on the ISS every day for 60 days—between January and March 2022—to determine how they were being used. These images go beyond interviewing astronauts to see how they adapt to such an unusual working/living situation. The human mind being what it is, interviews can leave out details that might seem irrelevant but are actually revealing.
The research article in PLOS One concerns two of the six areas: the latrine/exercise equipment area and the maintenance area.
This cutaway image of the International Space Station’s US Orbital Segment shows the locations of Square 03 (at upper center, in yellow) and 05 (at lower right, in orange). Square 03 is the maintenance area, and Square 05 is the latrine/exercise area. Image Credit: Walsh et al. 2024.“Using the photographs and an innovative web tool, we identified 5,438 instances of items, labelling them by type and function,” the authors explain in their research article. The ‘artifacts’ in the images included Post-It notes, writing tools, and an augmented reality headset. The research also includes astronaut activity reports which allowed for chronological cross-referencing.
This image shows Square 03 in the starboard Maintenance Work Area of the International Space Station. An open crew berth is on the right. The researchers developed an image analysis platform to process the images and identify artifacts. Image Credit: Walsh et al. 2024.The results show that an area near the latrine/exercise space without a designated purpose was used to store toiletries, resealable bags, and a seldom-used computer. The maintenance area was repurposed. No maintenance was done there, and the space was mostly used for storage.
This image shows Square 05, the latrine/exercise area. The Advanced Resistive Exercise Device is at the far upper right on the overhead wall. The Treadmill with Vibration Isolation Stabilization System is outside of the image on the left. The Waste and Hygiene Compartment is directly behind the photographer. Image Credit: Walsh et al. 2024.“One of the project goals is understanding cultural adaptations to the microgravity environment,” the authors explain in their research. They were especially interested in what they call ‘gravity surrogates,’ simple items used to keep things in their place. On Earth, we can just set a pen down on our desk, and it stays there until we need it again. But in microgravity, astronauts have to adapt.
The image of Square 05 shows an example of how astronauts adapt to their surroundings in unforeseen ways. The blue bar is a metal handrail used to help astronauts move around the ISS, but as NASA acknowledges, “they also serve as convenient locations for temporary mounting, affixing, or restraint of loose equipment and as attachment points for equipment.” The blue bar is just one of many examples of things with other uses serving as restraints in microgravity.
This figure from the research shows the number and type of artifacts in square 03. Restraints are the most plentiful objects. Image Credit: Walsh et al. 2024.SQuARE shows how spaces get used in unintended ways. Square 03 was intended for maintenance work but is used differently. “But much of the time, there was nobody working here—a fact that is not captured by historic photos of the area precisely because nothing is happening,” the authors explain.
Instead it’s used as a pegboard, like one mounted on a wall in a home. It’s a convenient place to store all types of items, some of which aren’t even used in the space because there are so many attachment points.
The authors say that their work provides “insights into material culture,” and that their results can be used in future spacecraft design. They can also help them study the rest of the squares more effectively.
“The experiment is the first archaeology ever to happen off of the planet Earth. By applying a very traditional method for sampling a site to a completely new kind of archaeological context, we show how the ISS crew uses different areas of the space station in ways that diverge from designs and mission plans. Architects and planners of future space stations can learn valuable lessons from this work,” the researchers conclude.
The post Archaeological Methods Reveal How Astronauts Work on the International Space Station appeared first on Universe Today.
