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P&R Labpak - Everything for your laboratory
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Tuesday, 29 December 2015

On this day in history: Krakatoa erupted

In 1927, Krakatoa began a new volcanic eruption on the seafloor along the same line as the cones of previous activity. By 26 Jan 1928, a growing cone had reached sea level and formed a small island called Anak Krakatoa (Child of Krakatoa). Sporadic activity continued until, by 1973, the island had reached a height of 622 ft above sea level. It was still in eruption in the early 1980s. The volcano Krakatoa is on Pulau (island) Rakata in the Sunda Strait between Java and Sumatra, Indonesia. It had been quiet since its previous catastrophic eruption of 1883. That threw sulphur and pumice 33 miles high and 36,380 people were killed either by the ash fall or by the resulting tidal wave. The only earlier known eruption was in 1680, and was only moderate.

Volcano, by ISS Crew Earth Observations experiment and the Image Science & Analysis Group, Johnson Space Center. [Public domain], via Wikimedia Commons
The combination of pyroclastic flows, volcanic ash, and tsunamis had disastrous results in the region. There were no survivors from the 3,000 people located on the island of Sebesi, about 13 km (8.1 mi) from Krakatoa. Pyroclastic flows killed around 1,000 people at Ketimbang on the coast of Sumatra some 48 km (30 mi) north from Krakatoa. The official death toll recorded by the Dutch authorities was 36,417, although some sources put the estimate at 120,000 or more. Many settlements were destroyed, including Teluk Betung (Bandar Lampung), and Sirik and Serang in Java. The areas of Banten on Java and Lampung on Sumatra were devastated. There are numerous documented reports of groups of human skeletons floating across the Indian Ocean on rafts of volcanic pumice and washing up on the east coast of Africa, up to a year after the eruption. Some land on Java was never repopulated; it reverted to jungle, and is now the Ujung Kulon National Park.

Ships as far away as South Africa rocked as tsunamis hit them, and the bodies of victims were found floating in the ocean for months after the event. The tsunamis which accompanied the eruption are believed to have been caused by gigantic pyroclastic flows entering the sea; each of the four great explosions was accompanied by massive pyroclastic flows resulting from the gravitational collapse of the eruption columns.This caused several cubic kilometers of material to enter the sea, displacing an equally huge volume of seawater. The town of Merak was destroyed by a tsunami 46 m (151 ft) high. Some of the pyroclastic flows reached the Sumatran coast as much as 40 km (25 mi) away, having apparently moved across the water on a cushion of superheated steam. There are also indications of submarine pyroclastic flows reaching 15 km (9.3 mi) from the volcano.

Smaller waves were recorded on tidal gauges as far away as the English Channel. These occurred too soon to be remnants of the initial tsunamis, and may have been caused by concussive air waves from the eruption. These air waves circled the globe several times and were still detectable on barographs five days later.

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Tuesday, 22 December 2015

New Mars rover findings revealed - much higher concentrations of silica indicate 'considerable water activity'

New findings by NASA's Mars Curiosity rover are the focus of a press conference this morning at the American Geophysical Union (AGU) meeting in San Francisco, Calif. A group of scientists, including one from Los Alamos National Laboratory, revealed that the Curiosity rover found much higher concentrations of silica at some sites the rover has investigated in the past seven months than anywhere else it has visited since landing on Mars 40 months ago. Silica makes up nine-tenths of the composition of some of the rocks.

Mars, by NASA, ESA, and The Hubble Heritage Team (STScI/AURA)
"The high silica was a surprise," said Jens Frydenvang of Los Alamos National Laboratory and the University of Copenhagen, also a Curiosity science team member. "While we're still working with multiple hypotheses on how the silica got so enriched, these hypotheses all require considerable water activity, and on Earth high silica deposits are often associated with environments that provide excellent support for microbial life. Because of this, the science team agreed to make a rare backtrack to investigate it more."

The first discovery was as Curiosity approached the area "Marias Pass," where a lower geological unit contacts an overlying one. ChemCam, the rover's laser-firing instrument for checking rock composition from a distance, detected bountiful silica in some targets the rover passed along the way to the contact zone. The ChemCam instrument was developed at Los Alamos in partnership with the French IRAP laboratory in Toulouse and the French Space Agency.

Adding information about silica clues was a major emphasis in rover operations over a span of four months and a distance of about one-third of a mile (half a kilometer). It involves many more readings from ChemCam, plus elemental composition measurements by the Alpha Particle X-ray Spectrometeter (APXS) on the rover's arm and mineral identification of drilled rock-powder samples analyzed by the Chemistry and Mineralogy (CheMin) instrument inside the rover.

Curiosity's science team is working with two main hypotheses to explain the recent findings on Mount Sharp, both of which require water. Water that is acidic would tend to carry other ingredients away and leave silica behind. Alkaline or neutral water could bring in dissolved silica that would be deposited from the solution. Apart from presenting a puzzle about the history of the region where Curiosity is working, the recent findings on Mount Sharp have intriguing threads to what an earlier rover, Spirit, found halfway around Mars. There, signs of sulfuric acidity were observed.

Adding to the puzzle, some of the silica found at one rock Curiosity drilled, called "Buckskin," is in a mineral named tridymite, which is found in Bandelier tuff, common in New Mexico but rare elsewhere, and never before seen on Mars. The usual origin of tridymite on Earth involves high temperatures in igneous or metamorphic rocks, but the finely layered sedimentary rocks examined by Curiosity have been interpreted as lakebed deposits.

Curiosity has been studying geological layers of Mount Sharp, starting from the bottom, since 2014, following two years of productive work on the plains surrounding the mountains. The mission delivered evidence in its first year that lakes in the area billions of years ago offered favorable conditions for life, if microbes ever lived on Mars. As Curiosity studies successively younger layers up Mount Sharp's slopes, the mission is investigating how ancient environmental conditions evolved from lakes, rivers and deltas to the harsh aridity of today's Mars.

Buckskin was the first of three rocks where drilled samples were collected during that period. The CheMin identification of tridymite prompted the team to look at possible explanations for it: "We could solve this by determining whether trydymite in the sediment comes from a volcanic source or has another origin," said Liz Rampe, of Aerodyne Industries at NASA's Johnson Space Center. "A lot of us are in our labs trying to see if there's a way to make tridymite without such a high temperature."

Beyond Marias Pass, ChemCam and APXS readings showed a pattern of high silica in pale zones along fractures in the bedrock, linking the silica enrichment there to alteration by fluids that flowed through the fractures and permeated into the bedrock. CheMin analyzed drilled material from a target called "Big Sky" in bedrock away from a fracture and from a fracture-zone target called "Greenhorn." Greenhorn indeed has much more silica, but not any in the form of tridymite. Much of it is in the form of noncrystalline opal, which can form in many types of environments, including hot springs, acid leaching and other wet settings.

"What we're seeing on Mount Sharp is dramatically different from what we saw in the first two years of the mission," said Curiosity Project Scientist Ashwin Vasavada of JPL. "There's so much variability within relatively short distances. The silica is one indicator of how the chemistry changed. It's such a multifaceted and curious discovery, we're going to take a while figuring it out."

The ChemCam has just passed 300,000 laser shots on Mars, each of which returns a color spectrum of the resulting plasma.

For more about Curiosity, which is examining sand dunes this month, visit the Mars Science Laboratory webpage: mars.jpl.nasa.gov/msl/

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Tuesday, 15 December 2015

Tim Peake: How the UK astronaut gets to space and back

UK astronaut Tim Peake will travel to the International Space Station (ISS) on 15 December. Since the space shuttle's retirement, the Russian Soyuz launch system is now the only way for crew members to get to the ISS.

The basic design for the Soyuz capsule was laid down as far back as the 1960s. It was originally intended to serve as the craft that would carry cosmonauts to the Moon.

When the US beat them to the lunar surface in 1969, the USSR's lunar programme was scrapped. But the Soyuz was retained, and became the Soviet - and subsequently Russian - vehicle of choice for launching humans to low-Earth orbit.

It was the craft that carried the first crew to the International Space Station in 2000, and has been the only craft ferrying humans to the orbiting outpost since the retirement of the US space shuttle in 2011.

"International Space Station after undocking of STS-132" by NASA/Crew of STS-132 -Licensed under Public Domain via Commons 
The current version, known as the Soyuz-TMA, can transport up to three cosmonauts and a limited amount of cargo to and from the ISS. At least one Soyuz is docked to the space station at all times to be used as a lifeboat in an emergency.

At one end of the spacecraft is the spherical orbital module. It's about the size of a large van and provides extra living space for the crew during flight. It can be used to store supplies and other cargo, such as experiments, and there's also a toilet.

The orbital module contains the mechanism used to dock with the space station and the hatch that allows crew members to enter the ISS.

The craft's mid-section is known as the descent module, and is where crew members sit during launch and the journey back to Earth. It contains the spacecraft's controls and displays, including a periscope that allows the crew to see the docking target on the ISS.

The seats have custom-fitted liners, individually moulded to each person's body. This is designed to help cushion the crew members when they land on Earth after a mission.

The third module is known as the instrument module. It contains the thrusters, oxygen and propellant tanks, communications equipment and the onboard computer.

Launched from Baikonur Cosmodrome in Kazakhstan, the 50m-high launcher consists of three sections, or stages. The first stage consists of four identical liquid-booster rockets. These are strapped around the core, or second, stage. The third, or upper, stage carries the Soyuz spacecraft.

The vehicle uses refined kerosene and liquid oxygen as fuel and can deliver payloads of more than seven tonnes - about the weight of a small lorry - into orbit.

Crew members enter the spacecraft two-and-a-half hours before launch to prepare it. At T-minus zero, the four boosters and core engine ignite, propelling the rocket into the air. About two minutes into the flight, the four booster rockets are jettisoned.

The core stage keeps firing, until it too separates at about 4 minutes 48 seconds after launch. A third stage engine then propels the Soyuz to its desired orbit at an altitude of some 220km. During the nine-minute sequence, crew members have to withstand forces up to three-and-a-half times their bodyweight.

The spacecraft then has to perform five engine burns in order to catch up with the ISS. This generally takes six hours, but if things don't go as planned, mission control may decide to fall back to an alternative two-day transfer mode.

Rendezvous and docking with the space station is automated by the onboard computer. It keeps track of the positions of the Soyuz and ISS using measurements from mission control and a radar system called Kurs. However, crew members closely monitor the process and have the ability to intervene or take over manual control if required.

During the final approach, a docking probe on the end of the Soyuz inserts into a cone on the ISS. Once "capture" is confirmed, the docking probe retracts, bringing the two vehicles together. A series of hooks and latches then close over, securing the Russian capsule to the ISS.

Once a tight seal is confirmed, the air pressure in the Soyuz is equalised with that of the ISS and the hatch is opened, so the new arrivals can enter the station.

When crew members are ready to return to Earth, a command is given to start opening the hooks and latches that hold the Soyuz to the ISS. The spacecraft then separates from the space station at a graceful speed of 10cm/s (4ins/s). Once the Soyuz has reached a distance of 20m (66ft) the Soyuz fires its thrusters for 15 seconds.

When the capsule reaches a distance of 19km (12mi) from the ISS, the Soyuz makes its main "de-orbit burn", firing the engines for 4 minutes, 21 seconds to begin the return to Earth. The descent module carrying the crew separates from the empty orbital module which burns up in the atmosphere.

About 15 minutes before landing, the capsule deploys a drogue parachute to slow its descent speed from 230m/s (755 ft/s) to 80m/s (262 ft/s). The main parachute is then released, cutting the capsule's speed to 7 m/s (24ft/s) and shifting it to a vertical position.

Six engines fire on the underside of the capsule to cushion the craft just before it thuds down on the Kazakh steppe.

A recovery and rescue team then arrives to extract the crew members.

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Tuesday, 8 December 2015

Levels of mercury in dolphins linked to exposure in humans, groundbreaking study finds

What do mercury levels in dolphins say about mercury levels in humans? Quite a bit, according to a new study by scientists at FAU Harbor Branch, which sheds light on the potential dangers of consuming locally caught seafood.

This is the first time that researchers have closed the loop between marine mammal and human health, by taking findings from their research and applying them to explore the potential risks facing humans living in the same region.

The study centers around dolphins living in the Indian River Lagoon (IRL), Florida and humans who live along the estuary and consume much of the same seafood as the dolphins. Initial studies of IRL dolphins showed high levels of mercury, which led scientists to conduct a follow-up study of humans who live in the same geographic area. The most toxic form of mercury known as methylmercury builds up in fish, shellfish, and animals that eat fish, and are the main sources of mercury exposure in humans.

Dolphin by NASAs [Public domain], via Wikimedia Commons

The findings from this study, published in the current issue of the journal Veterinary Sciences, showed that the cross-section of people tested also had high levels of mercury and that much of that mercury was due to consumption of locally obtained fish and shellfish. More than half of the participants in the study had a concentration of mercury in their hair, which was greater than the guideline for exposure defined by the U.S. Environmental Protection Agency.

"This research exemplifies the role of dolphins as an animal sentinel in identifying a public health hazard," said Adam Schaefer MPH, FAU Harbor Branch epidemiologist. "It is a unique and critical example of closing the loop between animal and human health."

Mercury is an important global health problem, most of which is due to consumption of fish and shellfish that become contaminated through the food web. The major human health risk results from high exposure during pregnancy, since the developing nervous system of a fetus is highly vulnerable to environmental insults such as maternal exposure to mercury. Long-term effects have been shown in poorer performance on standardized tests of learning, memory, visual-motor skills and cognitive development in multiple studies around the world.

"Fish consumption is recommended for a healthy diet and has many benefits including a reduction in the risk of developing cardiovascular disease," said John Reif, D.V.M., Colorado State University research professor and collaborator on the study. "Pregnant women can balance the risks and benefits of seafood consumption by continuing to eat fish, but avoiding fish caught in the Indian River Lagoon where the levels of mercury are higher."

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Wednesday, 2 December 2015

On this day in history: the first manned voyage of a hydrogen balloon left Paris

In 1783, the first manned voyage of a hydrogen balloon left Paris carrying Professor Jacques Alexander Cesar Charles and Marie-Noel Robert to about 600 m and landed 43 km away after 2 hours in the air.

Robert then left the balloon, and Charles continued the flight briefly to 2700 m altitude, measured by a barometer. This hydrogen-filled balloon was generally spherical and used a net, load ring, valve, open appendix and sand ballast, all of which were to be universally adopted later. His hydrogen generator mixed huge quantities of sulfuric acid with iron filings.

On 27 Aug 1783, Charles had launched an unmanned hydrogen balloon, just before the Montgolfiers' flight.

Hot air balloon, by Kropsoq (photo taken by Kropsoq) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/), CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5) or CC BY-SA 2.1 jp (http://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)], via Wikimedia Commons
There are three main types of balloon:

The hot air balloon or Montgolfière obtains its buoyancy by heating the air inside the balloon; it has become the most common type.

The gas balloon or Charlière is inflated with a gas of lower molecular weight than the ambient atmosphere; most gas balloons operate with the internal pressure of the gas the same as the pressure of the surrounding atmosphere; a superpressure balloon can operate with the lifting gas at pressure that exceeds that of the surrounding air, with the objective of limiting or eliminating the loss of gas from day-time heating; gas balloons are filled with gases such as:

  • Hydrogen – originally used extensively but, since the Hindenburg disaster, is now seldom used due to its high flammability;
  • Coal gas – although giving around half the lift of hydrogen, extensively used during the nineteenth and early twentieth century, since it was cheaper than hydrogen and readily available;
  • Helium – used today for all airships and most manned gas balloons;
Other gases have included ammonia and methane, but these have poor lifting capacity and other safety defects and have never been widely used.

The Rozière type has both heated and unheated lifting gases in separate gasbags. This type of balloon is sometimes used for long-distance record flights, such as the recent circumnavigations, but is not otherwise in use.

Both the hot air, or Montgolfière, balloon and the gas balloon are still in common use. Montgolfière balloons are relatively inexpensive, as they do not require high-grade materials for their envelopes, and they are popular for balloonist sport activity.

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