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).
Source: https://www.nasa.gov/feature/jpl/the-first-global-geologic-map-of-titan-completed
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.
Source: https://news.illinois.edu/view/6367/804723
Jounal article: https://www.pnas.org/content/116/42/20850
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.
Source: https://carnegiescience.edu/news/tendon-stem-cells-could-revolutionize-injury-recovery
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
Source: https://www.nasa.gov/image-feature/astronauts-complete-2nd-phase-to-repair-alpha-magnetic-spectrometer
