Saturday, November 30, 2019
The first map of the global geology of Saturn’s largest moon, Titan, has been completed, revealing a dynamic world with dunes, lakes, plains, craters and other terrains. The map is based on data from the international Cassini mission, which performed more than 120 flybys of Titan during its time at the Saturn system, between 2004 and 2017.
With a size comparable to that of Mercury, this moon is the only planetary body in our Solar System – besides Earth – known to have stable liquid on its surface. But instead of water raining down from clouds and filling lakes and seas as on Earth, what rains down on Titan and fills its liquid pools is methane and ethane.
This hydrocarbon-based hydrologic cycle has been shaping Titan’s complex geologic landscape, giving rise to the variety of terrains shown in this map. These include plains, which are broad, relatively flat regions (shown in pale green), labyrinths, which refer to tectonically disrupted regions often containing fluvial channels (shown in pink), hummocky, corresponding to hilly terrains, featuring some mountains (shown in pale orange), dunes, which are mostly linear and produced by winds on Titan’s surface (shown in purple), impact craters (shown in red), and lakes, currently or previously filled with liquid methane or ethane (shown in blue).
As evident in the map, different geologic terrains have a clear distribution with latitude, with dunes being most prominent around the equator, plains at mid-latitudes and labyrinth terrains and lakes towards the poles. The names of several surface features are indicated on an annotated version of the map, along with the landing site of ESA’s Huygens probe, which landed on Titan on 14 January 2005 as part of the Cassini mission.
To compile this map, scientists relied on a combination of radar, visual, and infrared data gathered by Cassini, in order to penetrate Titan’s thick and hazy atmosphere and identify surface features. The study, led by Rosaly Lopes of NASA’s Jet Propulsion Laboratory and also involving ESA research fellow Anezina Solomonidou, enabled the scientists to estimate the relative age of different geological units, indicating that dunes and lakes are relatively young, whereas the hummocky or mountainous terrains are the oldest on Titan. The results were recently published in Nature Astronomy.
The map is in Mollweide projection and has a scale of 1:20,000,000.
The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency (ESA) and the Italian Space Agency (ASI).
Research from the University of Illinois and the University of California, Davis has chemists one step closer to recreating nature’s most efficient machinery for generating hydrogen gas. This new development may help clear the path for the hydrogen fuel industry to move into a larger role in the global push toward more environmentally friendly energy sources.
The researchers report their findings in the Proceedings of the National Academy of Sciences.
Currently, hydrogen gas is produced using a very complex industrial process that limits its attractiveness to the green fuel market, the researchers said. In response, scientists are looking toward biologically synthesized hydrogen, which is far more efficient than the current human-made process, said chemistry professor and study co-author Thomas Rauchfuss.
Biological enzymes, called hydrogenases, are nature’s machinery for making and burning hydrogen gas. These enzymes come in two varieties, iron-iron and nickel-iron — named for the elements responsible for driving the chemical reactions. The new study focuses on the iron-iron variety because it does the job faster, the researchers said.
The team came into the study with a general understanding of the chemical composition of the active sites within the enzyme. They hypothesized that the sites were assembled using 10 parts: four carbon monoxide molecules, two cyanide ions, two iron ions and two groups of a sulfur-containing amino acid called cysteine.
The team discovered that it was instead more likely that the enzyme’s engine was composed of two identical groups containing five chemicals: two carbon monoxide molecules, one cyanide ion, one iron ion and one cysteine group. The groups form one tightly bonded unit, and the two units combine to give the engine a total of 10 parts.
But the laboratory analysis of the lab-synthesized enzyme revealed a final surprise, Rauchfuss said. “Our recipe is incomplete. We now know that 11 bits are required to make the active site engine, not 10, and we are in the hunt for that one final bit.”
Team members say they are not sure what type of applications this new understanding of the iron-iron hydrogenase enzyme will lead to, but the research could provide an assembly kit that will be instructive to other catalyst design projects.
“The take-away from this study is that it is one thing to envision using the real enzyme to produce hydrogen gas, but it is far more powerful to understand its makeup well enough to able to reproduce it for use in the lab,” Rauchfuss said.
Researchers from the Oregon Health and Science University also contributed to this study.
The National Institutes of Health supported this study.
Jounal article: https://www.pnas.org/content/116/42/20850
Friday, November 29, 2019
The buildup of scar tissue makes recovery from torn rotator cuffs, jumper’s knee, and other tendon injuries a painful, challenging process, often leading to secondary tendon ruptures. New research led by Carnegie’s Chen-Ming Fan and published in Nature Cell Biology reveals the existence of tendon stem cells that could potentially be harnessed to improve tendon healing and even to avoid surgery.
“Tendons are connective tissue that tether our muscles to our bones,” Fan explained. “They improve our stability and facilitate the transfer of force that allows us to move. But they are also particularly susceptible to injury and damage.”
Unfortunately, once tendons are injured, they rarely fully recover, which can result in limited mobility and require long-term pain management or even surgery. The culprit is fibrous scars, which disrupt the tissue structure of the tendon.
Working with Carnegie’s Tyler Harvey and Sara Flamenco, Fan revealed all of the cell types present in the Patellar tendon, found below the kneecap, including previously undefined tendon stem cells.
“Because tendon injuries rarely heal completely, it was thought that tendon stem cells might not exist,” said lead author Harvey. “Many searched for them to no avail, but our work defined them for the first time.”
Stem cells are “blank” cells associated with nearly every type of tissue, which have not fully differentiated into a specific functionality. They can also self-renew, creating a pool from which newly differentiated cell types can form to support a specific tissue’s function. For example, muscle stem cells can differentiate into muscle cells. But until now, stem cells for the tendon were unknown.
Surprisingly, the team’s research showed that both fibrous scar tissue cells and tendon stem cells originate in the same space — the protective cells that surround a tendon. What’s more, these tendon stem cells are part of a competitive system with precursors of fibrous scars, which explains why tendon healing is such a challenge.
The team demonstrated that both tendon stem cells and scar tissue precursor cells are stimulated into action by a protein called platelet-derived growth factor-A. When tendon stem cells are altered so that they don’t respond to this growth factor, then only scar tissue and no new tendon cells form after an injury.
“Tendon stem cells exist, but they must outcompete the scar tissue precursors in order to prevent the formation of difficult, fibrous scars,” Fan explained. “Finding a therapeutic way to block the scar-forming cells and enhance the tendon stem cells could be a game-changer when it comes to treating tendon injuries.
NASA astronaut Andrew Morgan is seen here tethered to the Starboard-3 truss segment work site during the second spacewalk to repair the International Space Station‘s cosmic particle detector, the Alpha Magnetic Spectrometer. During the 6.5 hour spacewalk, Morgan and Station Commander Luca Parmitano of the European Space Agency the two successfully cut eight stainless steel tubes, including one that vented the remaining carbon dioxide from the old cooling pump. The crew members also prepared a power cable and installed a mechanical attachment device in advance of installing the new cooling system.
This work clears the way for Parmitano and Morgan’s next spacewalk in the repair series Monday Dec. 2. The plan is to bypass the old thermal control system by attaching a new one off the side of AMS during the third spacewalk, and then conduct leak checks on a fourth spacewalk.
Image Credit: NASA