Tag Archives: #dry

Escape From Mars: How Water Fled The Red Planet (Planetary Science)

New UArizona-led research updates our understanding of how water escapes Mars – not like a leaky faucet but with a sudden splash.

Mars once had oceans but is now bone-dry, leaving many to wonder how the water was lost. University of Arizona researchers have discovered a surprisingly large amount of water in the upper atmosphere of Mars, where it is rapidly destroyed, explaining part of this Martian mystery.

This artist’s concept depicts the early Martian environment (right) – believed to contain liquid water and a thicker atmosphere – versus the cold, dry environment seen at Mars today (left). NASA’s Goddard Space Flight Center

Shane Stone, a graduate student in the UArizona Lunar and Planetary Laboratory and lead author of a new paper published today in Science, describes himself as a planetary chemist. Once a laboratory chemist who helped to develop polymers that could be used to wrap and deliver therapeutic drugs more efficiently, he now studies the chemistry of planetary atmospheres.

Since 2014, he has worked on the NASA MAVEN mission, short for Mars Atmosphere and Volatile EvolutioN. The MAVEN spacecraft began orbiting Mars in 2014 and has been recording the composition of the upper atmosphere of Earth’s planetary neighbor ever since.

“We know that billions of years ago, there was liquid water on the surface of Mars,” Stone said. “There must have been a thicker atmosphere, so we know that Mars somehow lost the majority of its atmosphere to space. MAVEN is trying to characterize the processes responsible for this loss, and one portion of that is understanding exactly how Mars lost its water.”

Co-authors of the study include Roger Yelle, a UArizona planetary sciences professor and Stone’s research adviser, as well as researchers from NASA Goddard Space Flight Center and the Center for Research and Exploration in Space Science and Technology in Maryland.

Watching for Water

As MAVEN orbits Mars, it dips into the planet’s atmosphere every 4 1/2 hours. The onboard NGIMS instrument, short for Neutral Gas and Ion Mass Spectrometer, has been measuring the abundance of charged water molecules called ions in the upper Martian atmosphere, about 100 miles from the planet’s surface. From this information, scientists can infer how much water is present in the atmosphere.

Past observations using MAVEN and the Hubble Space Telescope showed that loss of water from the Martian upper atmosphere varies with the seasons. Compared to Earth, Mars takes a more oval-shaped path around the sun and is closest to it during summer in the Martian southern hemisphere.

Stone and his team found that when Mars is nearest the sun, the planet warms, and more water – found on the surface in the form of ice – moves from the surface to the upper atmosphere where it is lost to space. This happens once every Martian year or about every two Earth years. The regional dust storms that occur on Mars every Martian year and the global dust storms that occur across the planet about once every 10 years lead to further heating of the atmosphere and a surge in the upward movement of water.

The processes that make this cyclical movement possible contradict the classical picture of water escape from Mars, showing it is incomplete, Stone said. According to the classical process, water ice is converted to a gas and is destroyed by the sun’s rays in the lower atmosphere. This process, however, would play out as a slow, steady trickle, unaffected by the seasons or dust storms, which doesn’t mesh with current observations.

“This is important because we didn’t expect to see any water in the upper atmosphere of Mars at all,” Stone said. “If we compare Mars to Earth, water on Earth is confined close to the surface because of something called the hygropause. It’s just a layer in the atmosphere that’s cold enough to condense (and therefore stop) any water vapor traveling upward.”

The team argues that water is moving past what should be Mars’ hygropause, which is likely too warm to stop the water vapor. Once in the upper atmosphere, water molecules are broken apart by ions very quickly – within four hours, they calculate – and the byproducts are then lost to space.

“The loss of its atmosphere and water to space is a major reason Mars is cold and dry compared to warm and wet Earth. This new data from MAVEN reveals one process by which this loss is still occurring today,” Stone said.

A Dry and Dusty World

When the team extrapolated their findings back 1 billion years, they found that this process can account for the loss of a global ocean about 17 inches deep.

“If we took water and spread it evenly over the entire surface of Mars, that ocean of water lost to space due to the new process we describe would be over 17 inches deep,” Stone said. “An additional 6.7 inches would be lost due solely to the effects of global dust storms.”

During global dust storms, 20 times more water can be transported to the upper atmosphere. For example, one global dust storm lasting 45 days releases the same amount of water to space as Mars would lose during a calm Martian year, or 687 Earth days.

And while Stone and his team can’t extrapolate farther back than 1 billion years, he thinks that this process likely didn’t work the same before that, because Mars might have had a stronger hygropause long ago.

“Before the process we describe began to operate, there must have been a significant amount of atmospheric escape to space already,” Stone said. “We still need to nail down the impact of this process and when it began to operate.”

In the future, Stone would like to study the atmosphere of Saturn’s moon, Titan.

“Titan has an interesting atmosphere in which organic chemistry plays a significant role,” Stone said. “As a former synthetic organic chemist, I’m eager to investigate these processes.”

References: http://dx.doi.org/10.1126/science.aba5229

Provided by University of Arizona

Red And Black Ink From Egyptian Papyri Unveil Ancient Writing Practices (Archeology)

Scientists led by the ESRF, the European Synchrotron, Grenoble, France and the University of Copenhagen, Denmark, have discovered the composition of red and black inks in ancient Egyptian papyri from circa 100-200 AD, leading to different hypotheses about writing practices. The analysis, based on synchrotron techniques, shows that lead was probably used as a dryer rather than as a pigment, similar to its usage in 15th century Europe during the development of oil paintings. They publish their results today in PNAS.

Detail of a medical treatise (inv. P. Carlsberg 930) from the Tebtunis temple library with headings marked in red ink. Image credit: The Papyrus Carlsberg Collection. ©The Papyrus Carlsberg Collection.

In ancient Egypt, Egyptians used black ink for writing the main body of text, while red ink was often used to highlight headings, instructions or keywords. During the last decade, many scientific studies have been conducted to elucidate the invention and history of ink in ancient Egypt and in the Mediterranean cultures, for instance ancient Greece and Rome.

A team of scientists led by the ESRF, the European Synchrotron, and the University of Copenhagen used the powerful X-rays of the ESRF to study the red and black ink in papyri from the only large-scale institutional library known to have survived from ancient Egypt: the Tebtunis temple library. The samples studied in this research project are exceptional, not only because they derive from the famous Tebtunis temple library, but also because the analysis includes as many as 12 ancient Egyptian papyrus fragments, all inscribed with red and black inks.

“By applying 21st century, state-of-the-art technology to reveal the hidden secrets of ancient ink technology, we are contributing to the unveiling the origin of writing practices.”, explains Marine Cotte, scientist at the ESRF and co-corresponding author of the paper.

“Something very striking was that we found that lead was added to the ink mixture, not as a dye, but as a dryer of the ink, so that the ink would stay on the papyrus”, says Cotte. The researchers came to this conclusion because they did not find any other type of lead, like lead white or minium, which should be present if lead was used as a pigment. “The fact that the lead was not added as a pigment but as a dryer infers that the ink had quite a complex recipe and could not be made by just anyone.”, adds Thomas Christiansen, Egyptologist from the University of Copenhagen and co-corresponding author .

A papyrus fragment from a long astrological treatise (inv. P. Carlsberg 89) from the Tebtunis temple library and the ESRF X-ray fluorescence maps showing the distribution of iron (red) and lead (blue) in the red letters that write out the ancient Egyptian word for “star”. Image credit: The Papyrus Carlsberg Collection and the ESRF. ©The Papyrus Carlsberg Collection and the ESRF.

A surprising fact is that the ink recipe can be related to paint practices developed many centuries later during the Renaissance. “In the XV Century, when artists rediscovered the oil painting in Europe, the challenge was to dry the oil in a reasonable amount of time”, says Marine Cotte. “Painters realised that some lead compounds could be used as efficient dryers”, she explains.

This finding was only possible thanks to the different techniques the team used at the ESRF’s beamline ID21 to study the fragments of papyri. They combined several synchrotron techniques (micro X-ray fluorescence, micro X-ray diffraction and micro-infrared spectroscopy) to probe the chemical composition from the millimetre to the sub-micrometre scale to provide information not only on the elemental, but also on the molecular and structural composition of the inks. The scientists discovered that lead was associated to different elements: a complex mixture of lead phosphates, potassium lead sulphates, lead carboxylates and lead chlorides.

Expectedly, the scientists found that the red colour in the ink is given by the ochre. More surprisingly, they discovered that this red pigment is present as coarse particles while the lead compounds are diffused into papyrus cells, at the micrometre scale, wrapping the cell walls, and creating, at the letter scale, a coffee-ring effect around the iron particles, as if the letters were outlined. “We think that lead must have been present in a finely ground and maybe in a soluble state and that when applied, big particles stayed in place, whilst the smaller ones ‘diffused’ around them”, explains Cotte. In these halos, lead is associated with sulphur and phosphorus. The origin of these lead sulphates and phosphates, i.e. were they initially present in ink or did they form during ink alteration, remains an open question. If they were part of the original ink, understanding their role in the writing process is also puzzling and the motivation of on-going research.

The team that came to the ESRF brings together chemists, physicists and Egyptologists. Sine Larsen, former director of research at the ESRF and currently Emerita professor at the Department of Chemistry, University of Copenhagen, was the mastermind that put the group together, back in 2016, and has coordinated it ever since. Several publications later, the collaboration keeps going strong. “I am fascinated by this subject of research, but also by the very diverse profiles that make up this truly interdisciplinary and successful collaboration”, she says.

References: Thomas Christiansen, Marine Cotte, Wout de Nolf, Elouan Mouro, Juan Reyes-Herrera, Steven de Meyer, Frederik Vanmeert, Nati Salvadó, Victor Gonzalez, Poul Erik Lindelof, Kell Mortensen, Kim Ryholt, Koen Janssens, Sine Larsen, “Insights into the composition of ancient Egyptian red and black inks on papyri achieved by synchrotron-based microanalyses”, Proceedings of the National Academy of Sciences Oct 2020, 202004534; DOI: 10.1073/pnas.2004534117

Provided by European Synchrotron Radiation Facility

Earth’s Water May Have Come From Materials That Were Present In The Inner Solar System (Astronomy)

A new study done by Piani and colleagues reported that Earth’s water may have come from materials that were present in the inner solar system at the time the planet formed—instead of far-reaching comets or asteroids delivering such water. They determined that a type of meteorite called an enstatite chondrite contains sufficient hydrogen to deliver at least three times the amount of water contained in the Earth’s oceans, and probably much more.

Piece of the meteorite Sahara 97096 (about 10 cm long), an enstatite chondrite that contains about 0.5 weight % of water. If Earth formed entirely of this material, it would have received 23 times the total mass of water present in the Earth’s oceans. Credit: L. Piani, Museum of Natural History in Paris

Enstatite chondrites are entirely composed of material from the inner solar system—essentially the same stuff that made up the Earth originally.

The findings from this study are surprising because the Earth’s building blocks are often presumed to be dry. They come from inner zones of the solar system where temperatures would have been too high for water to condense and come together with other solids during planet formation.

The meteorites provide a clue that water didn’t have to come from far away.

The most interesting part of this discovery is that enstatite chondrites, which were believed to be almost ‘dry,’ contain an unexpectedly high abundance of water.

Enstatite chondrites are rare, making up only about 2 percent of known meteorites in collections.

But their isotopic similarity to Earth make them particularly compelling. Enstatite chondrites have similar oxygen, titanium and calcium isotopes as Earth, and this study showed that their hydrogen and nitrogen isotopes are similar to Earth’s, too. In the study of extraterrestrial materials, the abundances of an element’s isotopes are used as a distinctive signature to identify where that element originated.

The paper also proposes that a large amount of the atmospheric nitrogen—the most abundant component of the Earth’s atmosphere—could have come from the enstatite chondrites.

Coupling two analytical techniques—conventional mass spectrometry and secondary ion mass spectrometry (SIMS)—allowed researchers to precisely measure the content and composition of the small amounts of water in the meteorites.

Prior to this study, it was commonly assumed that these chondrites formed close to the sun. Enstatite chondrites were thus commonly considered ‘dry,’ and this frequently reasserted assumption has probably prevented any exhaustive analyses to be done for hydrogen.

References: Laurette Piani, Yves Marrocchi, Thomas Rigaudier, Lionel G. Vacher, Dorian Thomassin, Bernard Marty, “Earth’s water may have been inherited from material similar to enstatite chondrite meteorites”, Science 28 Aug 2020: Vol. 369, Issue 6507, pp. 1110-1113 DOI: 10.1126/science.aba1948 link: https://science.sciencemag.org/content/369/6507/1110 (2) Anne H. Peslier, “The origins of water”, Science 28 Aug 2020:
Vol. 369, Issue 6507, pp. 1058
DOI: 10.1126/science.abc1338 link: https://science.sciencemag.org/content/369/6507/1058