Archives par mot-clé : Mars

Giant waves of sand are moving on Mars

by K. Kornei, July 23, 2020 in ScienceAAAS

Researchers have spotted large waves of martian sand migrating for the first time. The discovery dispels the long-held belief that these “megaripples” haven’t moved since they formed hundreds of thousands of years ago. They’re also evidence of stronger-than-expected winds on the Red Planet.

It’s pretty staggering that humans can detect these changes on Mars, says Ralph Lorenz, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory who was not involved in the research. “We can now measure processes on the surface of another planet that are just a couple times faster than our hair grows.”

Megaripples are found in deserts on Earth, often between dunes. Waves in the sand spaced up to tens of meters apart, they’re a larger version of ripples that undulate every 10 centimeters or so on many sand dunes.

The researchers focused on two sites near the equator of Mars. They analyzed roughly 1100 megaripples in McLaughlin crater and 300 in the Nili Fossae region. They looked for signs of movement by comparing time-lapse images of each site—taken 7.6 and 9.4 years apart, respectively. Megaripples in both regions advanced by about 10 centimeters per year, the team reports in the Journal of Geophysical Research: Planets. That’s about how fast megaripples move in the Lut Desert of Iran.

It’s a surprise that megaripples move at all on Mars, says Jim Zimbelman, a planetary geologist at the Smithsonian Institution’s Air and Space Museum. Just a few decades ago, there was no evidence that sands on Mars were mobile, he says. “None of us thought that the winds were strong enough.”

Megaripples near a sand dune on Mars.


Impact-induced amino acid formation on Hadean Earth and Noachian Mars

by Takeuchi et al., June8, 2020 in SciReports Open Access


Abiotic synthesis of biomolecules is an essential step for the chemical origin of life. Many attempts have succeeded in synthesizing biomolecules, including amino acids and nucleobases (e.g., via spark discharge, impact shock, and hydrothermal heating), from reduced compounds that may have been limited in their availabilities on Hadean Earth and Noachian Mars. On the other hand, formation of amino-acids and nucleobases from CO2 and N2 (i.e., the most abundant C and N sources on Earth during the Hadean) has been limited via spark discharge. Here, we demonstrate the synthesis of amino acids by laboratory impact-induced reactions among simple inorganic mixtures: Fe, Ni, Mg2SiO4, H2O, CO2, and N2, by coupling the reduction of CO2, N2, and H2O with the oxidation of metallic Fe and Ni. These chemical processes simulated the possible reactions at impacts of Fe-bearing meteorites/asteroids on oceans with a CO2 and N2 atmosphere. The results indicate that hypervelocity impact was a source of amino acids on the Earth during the Hadean and potentially on Mars during the Noachian. Amino acids formed during such events could more readily polymerize in the next step of the chemical evolution, as impact events locally form amino acids at the impact sites.

Stromatolites on Mars?

by D. Middleton, April 15, 2020 in WUWT

Evidence is steadily mounting that Mars could have supported life in the past and there are tantalizing indications that the Red Planet might still support be microscopic organisms. So, unlike the Face on Mars and impact craters circled up on satellite images, there is reason to believe that geologic features resembling stromatolites, might actually be something like stromatolites… But, we can’t possibly know until astronauts bring Martian sedimentary rocks back home to Earth.

Lower Proterozic (2.3 billion)
Eastern Andies South of Cochabamba, District of Cochabamba, Bolivia, South America
Fossil Museum Dot Net

Scientists: Mars Has A 95% CO2 Atmosphere…But ‘There Is Little To Retain Heat On The Planet’

by K. Richard, December 2, 2019 in NoTricksZone

Earth’s atmosphere contains 400 ppm CO2 (0.04%). Mars has a 950,000 ppm (95%) CO2 atmosphere. But Mars has surface temperatures that are about -75°C colder on average than Earth’s because atmospheric density, or pressure, is the “game changer” largely determining planetary temperatures.

Surface temperatures on Mars

The average surface temperature of a planetary body is significantly determined by its distance from the Sun.

According to the NASA Jet Propulsion Laboratory, Mars is close enough to the Sun to have its surface temperatures reach 35°C (95°F) at the equator during summer.

During winter, however, the Martian temperature dips to -90°C (-130°F).

The average surface temperature for Mars is about -60°C (-80°F).

Mars: Oxygen-rich, life-supporting liquid water?

by California Institute of Technology, October 22, 2018 in ScienceDaily

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.

Ancient Mars had right conditions for underground life, new research suggests

by Brown University, September 24, 2018 in ScienceDaily/EPSL

A new study shows evidence that ancient Mars probably had an ample supply of chemical energy for microbes to thrive underground.

“We showed, based on basic physics and chemistry calculations, that the ancient Martian subsurface likely had enough dissolved hydrogen to power a global subsurface biosphere,” said Jesse Tarnas, a graduate student at Brown University and lead author of a study published in Earth and Planetary Science Letters. “Conditions in this habitable zone would have been similar to places on Earth where underground life exists.”

New research shows that ancient Mars likely had ample chemical energy to support the kinds of underground microbial colonies that exist on Earth.
Credit: NASA / JPL

The Medusae Fossae Formation as the single largest source of dust on Mars

by L. Ojha et al., July 20, 2018 in NatureCommunications (open access)

Transport of fine-grained dust is one of the most widespread sedimentary processes occurring on Mars today. In the present climate, eolian abrasion and deflation of rocks are likely the most pervasive and active dust-forming mechanism. Martian dust is globally enriched in S and Cl and has a distinct mean S:Cl ratio. Here we identify a potential source region for Martian dust based on analysis of elemental abundance data …

Clear as mud: Desiccation cracks help reveal the shape of water on Mars

by Geological Society of America and in Geology, April 19,2018 in ScienceDaily

.pdf of the article

In early 2017 scientists announced the discovery of possible desiccation cracks in Gale Crater, which was filled by lakes 3.5 billion years ago. Now, a new study has confirmed that these features are indeed desiccation cracks, and reveals fresh details about Mars’ ancient climate.

“We are now confident that these are mudcracks,” explains lead author Nathaniel Stein, a geologist at the California Institute of Technology in Pasadena. Since desiccation mudcracks form only where wet sediment is exposed to air, their position closer to the center of the ancient lake bed rather than the edge also suggests that lake levels rose and fell dramatically over time.