Evidence of a Declining Martian Hydrological Cycle Starting 3.7 Billion Years Ago at the Noachian/Hesperian Boundary

Insights into surface runoff on early Mars from paleolake basin morphology and stratigraphy

Authors:

Goudge et al

Abstract:

We present observations on the morphology and stratigraphy of more than 400 paleolake basins on Mars. We show that there are two distinct classes of Martian paleolake basins: (1) paleolakes fed by regionally integrated valley networks (N = 251), and (2) paleolakes fed by isolated inlet valleys not integrated into broader regional drainage systems (N = 174). We conclude that valley network–fed paleolakes primarily formed prior to approximately the Noachian-Hesperian boundary, ca. 3.7 Ga, while isolated inlet valley paleolakes primarily formed later in Martian history. All 174 isolated inlet valley paleolakes are closed-basin lakes; however, there are surprisingly few (31) valley network–fed closed-basin lakes compared to a large number (220) of valley network–fed open-basin lakes. This observation is consistent with declining levels of fluvial activity over time on the Martian surface. Our results imply that during the era of valley network formation, ∼90% of topographic basins breached by an inlet valley had sufficiently high ratios of water influx to losses to fill, overtop, and form an outlet valley. This conclusion provides an important constraint on the balance between surface runoff production and water losses on early Mars that must be satisfied by any model of the early Martian climate and hydrologic cycle.

Robopocalypse Report #79

Drones:

University of Nebraska is testing how to use drones for fire fighting.

 Some are using drones to detect explosives, like land mines.

Drone racing just became big enough ESPN signed a deal to broadcast the races.

Shooting down a drone is now a federal crime.

The balloon drones are coming!

NASA is testing a system for nation wide drone traffic control.

DJI has made its most powerful drone yet.

Drones are banned from London's air space during Obama's visit.

Some are hoping drone racing goes big.

It finally happened, a drone crashed into an airliner in London.

An insect has inspired a way for DJI drones to float on water.

Malawi is setting up a program to use drones to help speed up HIV testing.

Self driving cars:

The Mercedes self driving truck convoy successfully completed its road trip across Europe.

Self driving Fords use LIDAR to drive.

A company in Singapore is seeking to test its self driving cars as taxis.

Singapore is about to start testing autonomous taxi pods.

Beverly Hills might get a small fleet of self driving shuttles.

A RAND report claims it is impossible to test self driving cars enough to prove their safety.

GEOHOT claims its self driving car tech will be available by the end of the year.

China had a self driving car drive across China.

China's answer to Tesla is semi self driving already.

China might be answering Tesla, but Musk might be answering China's self driving bus.

Dubai is pushing for driverless cars.

3d Printing:

Who is liable with 3d printed products?

The Foodini gets hyped more.

3d printed robotic birds used to scare away real birds.

What is the future of intellectual property with 3d printing?

The push for fashion to be 3d printed is on.

3d printed home contest winners have been announced.

Robotics:

Google owned Schaft has unveiled what looks like the ancestor of TARS from the movie, Interstellar.

Kongberg Marine seems to be out to freak out all the snake -phobes with the robopocalypse.

IBM has placed its Watson software bot in a robot body...much happened afterwards.

Underwater robots have been around for a long time.  Now they are being used in Lake Yellowstone for exploration.

Darmouth researchers have developed a robotic mural painter.

There is a new type of gripper.

Robots are helpful for rehab for the young.

A UUV found a prop from a Nessie movie.

Hitachi wants robots to help with the shopping.

Dispatch aims to have a fleet of delivery bots and have started testing.

This bot maps and does inventory of stores.

There's a mini bot intended to photograph your aquarium fish now.  hmm.

A new algorithm from MIT helps bots build a consensus to avoid obstacles.

Is Siemens the secret HQ of Dr Evil?  Their 3d printed spider robots make me wonder.

Robot butlers are being marketed by a Chinese company.

Software Bots:

Facebook is about unleash its own chatbots.  Tay was a lesson I hope they have learned from Microsoft!  More info.

Bots might be useful for treating social disorders.

Soon we might be texting bots as much as we do our friends.

There is a machine learning app now.

Another Microsoft bot isn't doing so well.

The next big gaming challenge for AI after chess & Go is now...Starcraft.

Cyborgism:

An implanted chip allowed a paralyzed man to control his hands.

Economics & Philosophy:

Why Robots need to be able to say 'no.'

Does automation help us or steal our sense of self?

US Army's Multi Mission Launcher Test Fired Missile From Israeli Iron Dome System

The Israeli Iron Dome missile system completed a successful test firing in the USA. The US Army completed a successful test of Tamir interceptor missile from the new Multi Mission Launcher (MML) developed under a US Army initiative. During the test the missile scored a hit at the target drone. RAFAEL and Raytheon plan to continue adapting the Iron Dome and Tamir interceptor missile to meet the requirements of the Indirect Fire Protection Capability (IFPC).

Prior to the test RAFAEL and its US partner Raytheon made the necessary adaptations to fit the Tamir missile with the Army experimental launcher. According to Lt. Col. Michael Fitzgerald, IFPC Inc 2-I Product Manager, the test was part of the US Army evaluation of different alternative effectors – both domestic and international, and their use with the Army’s new MML.

link.

some more photos.

Dental development in living and fossil orangutans

Dental development in living and fossil orangutans

Author:

Smith

Abstract:

Numerous studies have investigated molar development in extant and fossil hominoids, yet relatively little is known about orangutans, the only great ape with an extensive fossil record. This study characterizes aspects of dental development, including cuspal enamel daily secretion rate, long-period line periodicities, cusp-specific molar crown formation times and extension rates, and initiation and completion ages in living and fossil orangutan postcanine teeth. Daily secretion rate and periodicities in living orangutans are similar to previous reports, while crown formation times often exceed published values, although direct comparisons are limited. One wild Bornean individual died at 4.5 years of age with fully erupted first molars (M1s), while a captive individual and a wild Sumatran individual likely erupted their M1s around five or six years of age. These data underscore the need for additional samples of orangutans of known sex, species, and developmental environment to explore potential sources of variation in molar emergence and their relationship to life history variables. Fossil orangutans possess larger crowns than living orangutans, show similarities in periodicities, and have faster daily secretion rate, longer crown formation times, and slower extension rates. Molar crown formation times exceed reported values for other fossil apes, including Gigantopithecus blacki. When compared to African apes, both living and fossil orangutans show greater cuspal enamel thickness values and periodicities, resulting in longer crown formation times and slower extension rates. Several of these variables are similar to modern humans, representing examples of convergent evolution. Molar crown formation does not appear to be equivalent among extant great apes or consistent within living and fossil members of Pongo or Homo.

New interpretation of the wings of the pterosaur Rhamphorhynchus muensteri

New interpretation of the wings of the pterosaur Rhamphorhynchus muensteri based on the Zittel and Marsh specimens

Author:

Bennett

Abstract:

The Zittel wing of Rhamphorhynchus muensteri is reinterpreted as preserving negative impressions of closely spaced broad flat actinofibrils that were replaced by calcite but were prepared away by the specimen’s finder. The Marsh specimen preserves positive impressions of the dorsal and ventral surfaces of the wing, which show that the skin was smooth with fine wrinkles and that actinofibrils were not on the wing surface. Based on comparisons of those specimens, the dactylopatagium consisted of dorsal and ventral skins of epidermis and dermis surrounding a common hypodermis core, and keratinous actinofibrils developed in place within the dorsal epidermis adjacent to a layer of linear collagen fibers in the dorsal dermis. The actinofibrils and linear collagen fibers together formed the main functional structure of the dactylopatagium. That structure made the dactylopatagium somewhat stiff and essentially inextensible so that it folded up along discrete fold lines that probably were genetically determined. A pneumatic retrophalangeal wedge behind the antebrachium through at least wing phalanx 3 streamlined the transition between the thick wing spar and thin patagium.

The Implications of a Stromatolite From the Olenekian (Spathian) Triassic of China

Upper Lower Triassic stromatolite from Anhui, South China: Geobiologic features and paleoenvironmental implications

Authors:

Luo et al

Abstract:

Widespread stromatolites and other microbialite deposits characterize Lower Triassic marine successions worldwide. This study documents a stromatolite deposit, 1.1 m thick, from the upper Spathian (Lower Triassic) of the Susong area, South China. The stromatolite comprises distinct laminated domes in the basal part and columns at the upper part. Dark laminae are loosely spaced and interlayered with thicker light colored laminae. Diffusive dark colored laminae are composed of peloidal micrite that grade locally into microclotted structures, and yield copies of bacteria clump-like and coccoid-like spheroid aggregates. The former are characterized by cloudy, micrite nuclei rimmed by coarse-grained, euhedral sparry calcite crystals, while the latter are comprised of solid calcite crystal nuclei coated with rather thin micrite envelopes. The cloudy, micrite nuclei resemble bacteria clump-like structures observed in present-day travertine. Both the coccoid-like spheroids and bacteria clump-like structures are surrounded by coarse-grained euhedral calcite crystals, suggesting a similar accretion mechanism. Both spherical structures therefore could be crucial in the accretion of the Susong stromatolite. The laminated/microclotted structures are interpreted as the result of variation in timing of lithification relative to the timing of the decay of microbes. Micro-analysis also unravels the common occurrence of authigenic micro-quartz crystals in association with Fe-bearing illite clay minerals in the stromatolite columns. Their coalescing nature with each other, together with the associated pyrite grains, strongly support the formation of micro-quartz crystals from microbial reduction of an Fe-bearing smectite precursor by sulfate reducing bacteria. A comparison of the Susong stromatolite with its counterparts from the upper Lower Triassic strata in Dajiang, South China reveals many similarities in stromatolite microstructures, suggesting that a harsh, euxinic–anoxic environment resulting in the bloom of sulfate reducing bacteria most likely extended into the latest Spathian in South China.

Academic Bun Fight: Atmospheric Oxygen Levels During at the Calymmian/Ectasian MesoProterozoic Boundary

No evidence for high atmospheric oxygen levels 1,400 million years ago

Authors:

Planavsky et al

Abstract:

Zhang et al. (1) recently proposed atmospheric oxygen levels of ∼4% present atmospheric levels (PAL) based on modeling a paleoenvironment reconstructed from trace metal and biomarker data from the 1,400 Ma Xiamaling Formation in China. Intriguingly, this pO2 level is above the threshold oxygen requirements of basal animals and clashes with evidence for atmospheric oxygen levels much less than 1% PAL in the mid-Proterozoic (2). However, there are fundamental problems with the inorganic and organic geochemical work presented by Zhang et al. (1).

Zhang et al's reply:

Reply to Planavsky et al.: Strong evidence for high atmospheric oxygen levels 1,400 million years ago

Authors:

Zhang et al

Abstract:

Planavsky et al. (1) argue that variability in the V/Al of soils compromises our ability to detect V depletions and thus oxygenated bottom waters in the Xiamaling Formation. Indeed, because of such variability, we explored trace metal chemistry through several units of the Xiamaling Formation to establish V/Al background values and trace metal behavior. Unit 4 lacks trace metal enrichments, with V/Al values distributed around the crustal average (CA) (Fig. 1A), which we take to represent unaltered particles entering the basin. In contrast, unit 3 was enriched in Mo and U, with V/Al either depleted or similar to CA (Fig. 1A). These trace metal patterns are, in the modern ocean, uniquely found in organic-rich sediments depositing in oxygenated water (2).

Is Russia's 'Status-6' Dirty Bomb Robo Sub Real?

After making a splash in November, the Status-6 underwater drone has almost completely disappeared from the news. Probably for a good reason - the story looked like a deliberate fake from the beginning. And by all indications it was. Moreover, it appears that the appearance of that Status-6 slide on TV was an elaborate ploy that had something to do with an obscure internal power struggle in the Russian ministry of defense. Details are elusive and not particularly important, but the word is that the episode did result in some very high-level MoD officials being interrogated at Lefortovo regarding the alleged breach of security. Nothing came out of it, however.

That does not necessarily mean, however, that there is nothing behind the story. In February, a Russian newspaper published an article that mentioned Status-6 and included a photo that shows something that looks very much as a container that can house the drone on the slide:

link.

Why is Guatemala Building up its Military on the Belizean Border?!

The shooting death of a 13-year-old Guatemalan boy has provoked the largest border mobilization for the country in decades. On April 20, Belizean troops killed Julio Alvarado Ruano and wounded his father and brother, which Belizean authorities said occurred after the troops came under fire.

Guatemalan President Jimmy Morales called the shootings a “cowardly and excessive attack” and ordered some 3,000 soldiers to amass near the border — which has been disputed since before Belize’s independence from the United Kingdom in 1981. The mobilization focuses on the Adjacency Zone, a buffer region along the border marked by the Sarstoon River.

link.

Ukraine War Update: Упрямым слепцом Никогда не видите

Anyone who has been following the OSCE Monitoring Mission in Ukraine has known this for some time: the truce is a farce.  Some days there are over a thousand artillery shells lobbed around Donetsk...and that's what the OSCE reports.  They have been noted in the past to have very spotty coverage of the entire line of contact and most of that line has been aflame for some time.

The increase in fighting intensity began when the political meltdown in Kiev began.  IMO, Donnie Reb is hoping for a meltdown sufficient they can begin offensives again, since the weather is improving.  It should be remembered though: Kiev != the People of Ukraine. 

In the last 24 hours, 3 Ukrainian soldiers have been killed in the fighting.

Even Merkel is finally saying the truce is not being respected.

There have been a few protests against the government in Odessa.  However, they were fairly limited.

I have not been posting as much here, because for personal reasons, I do not have direct contact with the people on the ground in Ukraine any more.

Global Albedos of Pluto and Charon from LORRI New Horizons Observations

Global Albedos of Pluto and Charon from LORRI New Horizons Observations

Authors:

Burratti et al

Abstract:

The exploration of the Pluto-Charon system by the New Horizons spacecraft represent the first opportunity to understand the distribution of albedo and other photometric properties of the surfaces of objects in the Solar System's "Third Zone" within the context of a geologic world. Images of the entire illuminated surface of Pluto and Charon obtained by the Long Range Reconnaissance Imager (LORRI) camera provide a global map of Pluto that revealed surface albedo variegations larger than any other world except for Saturn's moon Iapetus. Normal reflectances on Pluto range from 0.08-1.0. Charon exhibits a much blander surface with normal reflectances ranging from 0.20-0.73. Pluto's albedo features are well-correlated with geologic features, although some exogenous low-albedo dust may be responsible for features seen to the west of the area informally named Tombaugh Regio. The albedo patterns of both Pluto and Charon are latitudinally organized, with the exception of Tombaugh Regio. The low-albedo areas of Pluto are darker than anything on Charon's surface. The phase curve of Pluto is similar to that of Triton, the large moon of Neptune, and a former KBO dwarf planet, while Charon's is similar to that of the Moon. Preliminary Bond albedos are 0.25 +/- 0.03 for Charon and 0.72 +/- 0.07 for Pluto. Maps of the Bond albedo for both Pluto and Charon are presented for the first time.

Present-day formation and seasonal evolution of linear dune gullies on Mars

Present-day formation and seasonal evolution of linear dune gullies on Mars

Authors:

Pasquon et al

Abstract:

Linear dune gullies are a sub-type of martian gullies. As their name suggests they only occur on sandy substrates and comprise very long (compared to their width) straight or sinuous channels, with relatively small source areas and almost non-existent visible deposits. Linear dune gullies have never been observed on terrestrial dunes and their formation process on Mars is unclear. Here, we present the results of the first systematic survey of these features in Mars’ southern hemisphere and an in-depth study of six dunefields where repeat-imaging allows us to monitor the changes in these gullies over time. This study was undertaken with HiRISE images at 25–30 cm/pix and 1 m/pix elevation data derived from HiRISE stereo images. We find the latitudinal distribution and orientation of linear dune gullies broadly consistent with the general population of martian gullies. They occur predominantly between 36.3°S and 54.3°S, and occasionally between 64.6°S and 70.4°S. They are generally oriented toward SSW (at bearings between 150° and 260°). We find that these gullies are extremely active over the most recent 5 Martian years of images. Activity comprises: (1) appearance of new channels, (2) lengthening of existing channels, (3) complete or partial reactivation, and (4) disappearance of gullies. We find that gully channels lengthen by ∼100 m per year. The intense activity and the progressive disappearance of linear dune gullies argues against the hypothesis that these are remnant morphologies left over from previous periods of high obliquity millions of years ago. The activity of linear dune gullies reoccurs every year between the end of winter and the beginning of spring (Ls 167.4°–216.6°), and coincides with the final stages of the sublimation of annual CO₂ ice deposit. This activity often coincides spatially and temporally with the appearance of recurrent diffusing flows (RDFs)—digitate-shaped, dark patches with low relative albedo (up to 48% lower than the adjacent dune) that encompass the active site. South- and SSW-facing dune slopes are those which preferentially host CO2 frost deposits, however, it is only those with angles of ∼20° just below the crest which possess linear dune gullies, suggesting a slope-limited formation process. These observations provide a wealth of temporal and morphometric data that can be used to undertake numerical modeling, to direct future image monitoring and guide laboratory experiments that can be used to better constrain the formation process of these features.

Coming Cyber War #8

Cyber Warfare:

US enemies can cyber attack US satellites. 

The US has been using cyber weapons against ISIL/Daesh.

Congress has set up an independent Cyber Command for the US military.

Cyber operations are being advocated as a way to offset the rise of China's power.

Israel & Singapore are working more closely together on cyber operations.

Cyber Security:

Australia has launched a major cyber hardening initiative.

The US government really sucks at cyber security.

The US DOD is prioritizing cyber hardening.

MIT has developed an AI that is 85% effective in detecting cyber attacks.  I wonder how it compares to BRO.

Cyber crime:

Cyber criminals have started adopting corporate best practices.

British Aerospace is warning of the QBOT malware.

Swedish military systems were hacked and used to attack US banking systems.

Russia Tested Project 4202, a Hypersonic Warhead

One of the Russian newspapers, MK, quotes its unnamed sources as saying that Russia conducted a flight test of a "hypersonic warhead" earlier this week (apparently on April 19). The missile carrying the warhead was launched from the Dombarovsky site. The test is said to be successful.

link.

China's Work on Hypersonic Weapons

China’s military is reorganizing itself to be a more modern, effective force. On January 1, 2016, the Second Artillery Force (第二炮兵部队) (responsible for China’s nuclear and conventional ballistic missile arsenals) was reorganized into the People’s Liberation Army Rocket Force (PLARF; 火箭部队), elevating it to a service (军种) fully on-par with the Navy, Army and Air Force (Sina, January 1). As China streamlines its military and works to improve the quality of its personnel, several cutting edge projects are in the works to provide the People’s Liberation Army with advanced weapons. One of these is the PRC’s hypersonic glide vehicle (HGV), called the DF-ZF in China and designated by U.S. defense officials as the Wu-14. The development and testing of this new class of hypersonic weaponry in China has been extremely secretive. However, its eventual operational deployment will represent a significant improvement in the PLARF’s conventional and nuclear arsenals, as it has the potential to penetrate even the strongest layered anti-missile defenses of the United States and its allies.

link.

Elaphrosaurus bambergi: a Reevaluated Noasaurid Abelisauroid From Late Jurassic Tanzania

The theropod dinosaur Elaphrosaurus bambergi Janensch, 1920, from the Late Jurassic of Tendaguru, Tanzania

Authors:

Rauhaut et al

Abstract:

Theropod dinosaurs from the Late Jurassic of Gondwana are still poorly known, with Elaphrosaurus bambergi Janensch, 1920, from the late Kimmeridgian of Tendaguru, Tanzania, being the only taxon represented by more than isolated remains from Africa. Having long been considered a coelurosaurian, more specifically an ornithomimosaur, Elaphrosaurus is currently regarded as a basal ceratosaur. Here, we revise the osteology and phylogenetic position of this important taxon. Elaphrosaurus shows many unusual osteological characters, including extremely elongated and constricted cervical vertebrae, an expansive shoulder girdle with strongly modified forelimbs, a relatively small ilium, and elongate hindlimbs with a very small ascending process of the astragalus that is fused to the tibia. We found this taxon to share many derived characters with noasaurids, such as: strongly elongate cervical and dorsal vertebrae; low, rectangular neural spines in the mid-caudal vertebrae; presence of only an anterior centrodiapophyseal lamina in anterior caudal vertebrae; presence of a wide, U–shaped notch between the glenoid and the anteroventral hook in the coracoid; a laterally flared postacetabular blade of the ilium; a flat anterior side of the distal tibia; and a reduced shaft of metatarsal II. Our analysis placed Elaphrosaurus within a dichotomous Noasauridae as part of a Jurassic subclade, here termed Elaphrosaurinae, that otherwise includes taxa from eastern Asia. These results underscore the long and complex evolutionary history of abelisauroids, which is still only beginning to be understood.

Glacial dropstones in the western Tethys during the late Aptian–early Albian cold snap

Glacial dropstones in the western Tethys during the late Aptian–early Albian cold snap: Palaeoclimate and palaeogeographic implications for the mid-Cretaceous

Authors:

Rodríguez-López et al

Abstract:

The late Jurassic–early Cretaceous is commonly considered the only cold climatic interval in Earth history without any direct evidence of polar ice. A newly discovered dropstone-bearing interval from the subtropical Iberian Basin (western Tethys) is described and provides evidence of contemporaneous polar glaciation. This interval is correlated laterally for 4.8 km and contains a boulder and two cobble-sized quartzite dropstones that are encased in mid-Cretaceous fissile black shales and fine-grained sandstones. Based on previously published dimensions of similar large clasts, only glacial dropstones and impact ejecta blocks reach the dimensions of the boulder-sized dropstone reported from Iberia. The dropstones show morphological features compatible with glacial transport and abrasion in a subglacial setting which closely resembles the features observed in recent glacial boulders exposed near the snouts of glaciers in Iceland. These Late Aptian dropstones from Spain correlate with many other similar erratics in the northern and southern palaeohemispheres, and suggest that ice sheets formed around the palaeo-North Pole during certain periods of the early Cretaceous. Our results and associated evidence such as the occurrence of glendonites, tillites, moderate- to high-amplitude sea-level oscillations worldwide, minimum pCO2 concentrations, variation in calcareous nannofossil assemblages from low and high latitudes and isotopic excursions suggest that during the mid-Cretaceous there were periods of ice growth and decay that influenced the palaeotemperature, palaeoecology and sedimentology of the marine realm. The new data from Iberia are supported by recent results from Arctic Canada that indicate cool shelves and a mid-Cretaceous cold snap that developed for ~ 6 Myr between 118 and 112 Ma. The late Aptian dropstones reported in eastern Iberia were likely transported from high northern latitudes towards subtropical ones in the western Tethys by an extreme iceberg drift similar to those occurring at the present day in the Atlantic Ocean. Icebergs released from a northern fringing ice sheet may have travelled southwards through the Greenland–Norwegian Seaway.

Lariosaurus vosseveldensis: a new Anisian Triassic Nothosaur Species From Germany

The earliest record of the genus Lariosaurus from the early middle Anisian (Middle Triassic) of the Germanic Basin

Authors:

Klein et al

Abstract:

A new skull representing the oldest record of the genus Lariosaurus in the Germanic Basin is described. The small-sized skull originates from the early middle Anisian (Bithynian) of the Winterswijkse Steengroeve (Winterswijk, The Netherlands) and is assigned to L. vosseveldensis, sp. nov. Supplementation of a recently established phylogeny with L. vosseveldensis, sp. nov., recovered it within Lariosaurus as the sister taxon to Nothosaurus winkelhorsti and L. buzzii. The generic assignment of N. juvenilis, N. youngi, and N. winkelhorsti to Nothosaurus must be reevaluated to reestablish support for a monophyletic Lariosaurus, and only a definitive resolution of the polytomy including Germanosaurus could recover a monophyletic Nothosauridae. The Winterswijk locality has previously yielded a rich and diverse marine reptile fauna, including an endemic basal placodont. The nearly contemporaneous occurrence of L. vosseveldensis, sp. nov., and L. hongguoensis from the middle Anisian (Pelsonian) of China indicates a very rapid dispersal of the group, but does not resolve the origin of Sauropterygia (eastern Tethyan faunal province vs. western Tethyan faunal province).

North Korea Attempted Submarine Launched Ballistic Missile on Saturday

North Korea on Saturday tested what appeared to be a submarine-launched ballistic missile in the Sea of Japan, the South Korean defence ministry said.

"North Korea launched a projectile which was believed to be a submarine-launched ballistic missile (SLBM) around 6:30 pm (0930 GMT) in the East Sea (Sea of Japan) near the northeastern port of Sinpo", a defence ministry spokesman said.

"We are keeping close tabs on the North Korean military and maintaining a full defence posture", he said.

The missile flew 30 kilometres (18 miles) but the launch "appeared to have failed," he added.

link.

UC Irvine Researchers Claim to Have Greatly Increased Lithium Ion Battery Life Times (over 100k cycles)

100k Cycles and Beyond: Extraordinary Cycle Stability for MnO2 Nanowires Imparted by a Gel Electrolyte

Authors:

Thai et al

Abstract:

We demonstrate reversible cycle stability for up to 200 000 cycles with 94–96% average Coulombic efficiency for symmetrical δ-MnO2 nanowire capacitors operating across a 1.2 V voltage window in a poly(methyl methacrylate) (PMMA) gel electrolyte. The nanowires investigated here have a Au@δ-MnO2 core@shell architecture in which a central gold nanowire current collector is surrounded by an electrodeposited layer of δ-MnO2 that has a thickness of between 143 and 300 nm. Identical capacitors operating in the absence of PMMA (propylene carbonate (PC), 1.0 M LiClO4) show dramatically reduced cycle stabilities ranging from 2000 to 8000 cycles. In the liquid PC electrolyte, the δ-MnO2 shell fractures, delaminates, and separates from the gold nanowire current collector. These deleterious processes are not observed in the PMMA electrolyte.