Monthly Archives: April 2017

On this day in science history: Pioneer 10 crossed the orbit of Pluto

In 1983, Pioneer 10, an
American space probe, crossed the orbit of Pluto, the outermost planet, to
continue its voyage into the universe beyond our solar system. This space
exploration project was conducted by the NASA Ames Research Center in
California, and the space probe was manufactured by TRW Inc.

Pioneer 10 was launched on
March 2, 1972, by an Atlas-Centaur expendable vehicle from Cape Canaveral,
Florida. Between July 15, 1972, and February 15, 1973, it became the first
spacecraft to traverse the asteroid belt. Photography of Jupiter began on November
6, 1973, at a range of 25,000,000 kilometres (16,000,000 mi), and a total of
about 500 images were transmitted. The closest approach to the planet was on
December 4, 1973, at a range of 132,252 kilometres (82,178 mi). During the
mission, the on-board instruments were used to study the asteroid belt, the
environment around Jupiter, the solar wind, cosmic rays, and eventually the far
reaches of the Solar System and heliosphere.

Artist’s impression of Pioneer 10’s flyby of Jupiter, by Rick Guidice [Public domain], via Wikimedia Commons
So, what do we know about
Jupiter?

Jupiter is the fifth planet
from the Sun and the largest in the Solar System. It is a giant planet with a
mass one-thousandth that of the Sun, but two and a half times that of all the
other planets in the Solar System combined. Jupiter and Saturn are gas giants;
the other two giant planets, Uranus and Neptune are ice giants. Jupiter has
been known to astronomers since antiquity. The Romans named it after their
god Jupiter. When viewed from Earth, Jupiter can reach an apparent
magnitude of −2.94, bright enough for its reflected light to cast shadows, and making it on average the third-brightest object in the night sky after the
Moon and Venus.

Jupiter is primarily composed
of hydrogen with a quarter of its mass being helium, though helium comprises
only about a tenth of the number of molecules. It may also have a rocky core of
heavier elements, but like the other giant planets, Jupiter lacks a
well-defined solid surface. Because of its rapid rotation, the planet’s shape
is that of an oblate spheroid (it has a slight but noticeable bulge around the
equator). The outer atmosphere is visibly segregated into several bands at
different latitudes, resulting in turbulence and storms along their interacting
boundaries. A prominent result is the Great Red Spot, a giant storm that is
known to have existed since at least the 17th century when it was first seen by
telescope. Surrounding Jupiter is a faint planetary ring system and a powerful
magnetosphere. Jupiter has at least 67 moons, including the four large Galilean
moons discovered by Galileo Galilei in 1610. Ganymede, the largest of these,
has a diameter greater than that of the planet Mercury.

Radio communications were lost
with Pioneer 10 on January 23, 2003, because of the loss of electric power for
its radio transmitter, with the probe at a distance of 12 billion kilometers
(80 AU) from Earth.

Jupiter has been explored on
several other occasions by robotic spacecraft, such as the Voyager flyby
missions and later, the Galileo orbiter. In late February 2007, Jupiter was
visited by the New Horizons probe, which used Jupiter’s gravity to increase its
speed and bend its trajectory en route to Pluto. The latest probe to visit the
planet is Juno, which entered into orbit around Jupiter on July 4, 2016. Future
targets for exploration in the Jupiter system include the probable ice-covered
liquid ocean of its moon Europa.

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Mission control: salty diet makes you hungry, not thirsty

We’ve all heard it: eating salty
foods makes you thirstier. But what sounds like good nutritional advice turns
out to be an old-wives’ tale. In a study carried out during a simulated mission
to Mars, an international group of scientists has found exactly the opposite to
be true. “Cosmonauts” who ate more salt retained more water, weren’t
as thirsty, and needed more energy.

Salt shaker, by Dubravko Sorić SoraZG on Flickr [CC BY 2.0 (http://ift.tt/o655VX)%5D, via Wikimedia Commons
For some reason, no one had ever
carried out a long-term study to determine the relationship between the amount
of salt in a person’s diet and his drinking habits. Scientists have known that
increasing a person’s salt intake stimulates the production of more urine – it
has simply been assumed that the extra fluid comes from drinking. Not so fast!
say researchers from the German Aerospace Center (DLR), the Max Delbrück Center
for Molecular Medicine (MDC), Vanderbilt University and colleagues around the
world. Recently they took advantage of a simulated mission to Mars to put the
old adage to the test. Their conclusions appear in two papers in the current
issue of The Journal of Clinical Investigation.

What does salt have to do with
Mars? Nothing, really, except that on a long space voyage conserving every drop
of water might be crucial. A connection between salt intake and drinking could
affect your calculations – you wouldn’t want an interplanetary traveler to die
because he liked an occasional pinch of salt on his food. The real interest in
the simulation, however, was that it provided an environment in which every
aspect of a person’s nutrition, water consumption, and salt intake could be
controlled and measured.

The studies were carried out by
Natalia Rakova (MD, PhD) of the Charité and MDC and her colleagues. The
subjects were two groups of 10 male volunteers sealed into a mock spaceship for
two simulated flights to Mars. The first group was examined for 105 days; the
second over 205 days. They had identical diets except that over periods lasting
several weeks, they were given three different levels of salt in their food.

The results confirmed that eating
more salt led to a higher salt content in urine – no surprise there. Nor was
there any surprise in a correlation between amounts of salt and overall
quantity of urine. But the increase wasn’t due to more drinking – in fact, a
salty diet caused the subjects to drink less. Salt was triggering a mechanism
to conserve water in the kidneys.

Before the study, the prevailing
hypothesis had been that the charged sodium and chloride ions in salt grabbed
onto water molecules and dragged them into the urine. The new results showed
something different: salt stayed in the urine, while water moved back into the
kidney and body. This was completely puzzling to Prof. Jens Titze, MD of the
University of Erlangen and Vanderbilt University Medical Center and his
colleagues. “What alternative driving force could make water move
back?” Titze asked.

Experiments in mice hinted that
urea might be involved. This substance is formed in muscles and the liver as a
way of shedding nitrogen. In mice, urea was accumulating in the kidney, where
it counteracts the water-drawing force of sodium and chloride. But synthesizing
urea takes a lot of energy, which explains why mice on a high-salt diet were
eating more. Higher salt didn’t increase their thirst, but it did make them
hungrier. Also the human “cosmonauts” receiving a salty diet
complained about being hungry.
The project revises scientists’
view of the function of urea in our bodies. “It’s not solely a waste
product, as has been assumed,” Prof. Friedrich C. Luft, MD of the Charité
and MDC says. “Instead, it turns out to be a very important osmolyte – a
compound that binds to water and helps transport it. Its function is to keep
water in when our bodies get rid of salt. Nature has apparently found a way to
conserve water that would otherwise be carried away into the urine by
salt.”

The new findings change the way
scientists have thought about the process by which the body achieves water
homeostasis – maintaining a proper amount and balance. That must happen whether
a body is being sent to Mars or not. “We now have to see this process as a
concerted activity of the liver, muscle and kidney,” says Jens Titze.

“While we didn’t directly
address blood pressure and other aspects of the cardiovascular system, it’s
also clear that their functions are tightly connected to water homeostasis and
energy metabolism.”

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The chemistry behind the new one pound coin

We all know that money makes the world go around, but do you know what goes into it? The new pound coin arrived on 28th March, largely as a preventative measure against counterfeiting.  Take a look at the graphic below for more information about its composition.

Source: Compound Interest

Why the new coin is harder to counterfeit
  1. 12-sided – its distinctive shape means it stands out by sight and by touch
  2. Bimetallic – The outer ring is gold coloured (nickel-brass) and the inner ring is silver coloured (nickel-plated alloy)
  3. Latent image – it has an image like a hologram that changes from a ‘£’ symbol to the number ‘1’ when the coin is seen from different angles
  4. Micro-lettering – around the rim on the heads side of the coin tiny lettering reads: ONE POUND. On the tails side you can find the year the coin was produced
  5. Milled edges – it has grooves on alternate sides
  6. Hidden high security feature – an additional security feature is built into the coin to protect it from counterfeiting but details have not been revealed

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New device produces hydrogen peroxide for water purification

Limited access to clean water is a major issue for billions of people in the developing world, where water sources are often contaminated with urban, industrial and agricultural waste. Many disease-causing organisms and organic pollutants can be quickly removed from water using hydrogen peroxide without leaving any harmful residual chemicals. However, producing and distributing hydrogen peroxide is a challenge in many parts of the world.

Purified drinking water
Now scientists at the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University have created a small device for hydrogen peroxide production that could be powered by renewable energy sources, like conventional solar panels.

“The idea is to develop an electrochemical cell that generates hydrogen peroxide from oxygen and water on site, and then use that hydrogen peroxide in groundwater to oxidize organic contaminants that are harmful for humans to ingest,” said Chris Hahn, a SLAC associate staff scientist.

Their results were reported March 1 in Reaction Chemistry and Engineering.
The project was a collaboration between three research groups at the SUNCAT Center for Interface Science and Catalysis, which is jointly run by SLAC and Stanford University.

“Most of the projects here at SUNCAT follow a similar path,” said Zhihua (Bill) Chen, a graduate student in the group of Tom Jaramillo, an associate professor at SLAC and Stanford. “They start from predictions based on theory, move to catalyst development and eventually produce a prototype device with a practical application.”

In this case, researchers in the theory group led by SLAC/Stanford Professor Jens Nørskov used computational modeling, at the atomic scale, to investigate carbon-based catalysts capable of lowering the cost and increasing the efficiency of hydrogen peroxide production. Their study revealed that most defects in these materials are naturally selective for generating hydrogen peroxide, and some are also highly active. Since defects can be naturally formed in the carbon-based materials during the growth process, the key finding was to make a material with as many defects as possible.

“My previous catalyst for this reaction used platinum, which is too expensive for decentralized water purification,” said research engineer Samira Siahrostami. “The beautiful thing about our cheaper carbon-based material is that it has a huge number of defects that are active sites for catalyzing hydrogen peroxide production.”

Stanford graduate student Shucheng Chen, who works with Stanford Professor Zhenan Bao, then prepared the carbon catalysts and measured their properties. With the help of SSRL staff scientists Dennis Nordlund and Dimosthenis Sokaras, these catalysts were also characterized using X-rays at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), a DOE Office of Science User Facility.

“We depended on our experiments at SSRL to better understand our material’s structure and check that it had the right kinds of defects,” Shucheng Chen said.

Finally, he passed the catalyst along to his roommate Bill Chen, who designed, built and tested their device.

“Our device has three compartments,” Bill Chen explained. “In the first chamber, oxygen gas flows through the chamber, interfaces with the catalyst made by Shucheng and is reduced into hydrogen peroxide. The hydrogen peroxide then enters the middle chamber, where it is stored in a solution.” In a third chamber, another catalyst converts water into oxygen gas, and the cycle starts over.

Separating the two catalysts with a middle chamber makes the device cheaper, simpler and more robust than separating them with a standard semi-permeable membrane, which can be attacked and degraded by the hydrogen peroxide.

The device can also run on renewable energy sources available in villages. The electrochemical cell is essentially an electrical circuit that operates with a small voltage applied across it. The reaction in chamber one puts electrons into oxygen to make hydrogen peroxide, which is balanced by a counter reaction in chamber three that takes electrons from water to make oxygen – matching the current and completing the circuit. Since the device requires only about 1.7 volts applied between the catalysts, it can run on a battery or two standard solar panels.

The research groups are now working on a higher-capacity device.

Currently the middle chamber holds only about 10 microliters of hydrogen peroxide; they want to make it bigger. They’re also trying to continuously circulate the liquid in the middle chamber to rapidly pump hydrogen peroxide out, so the size of the storage chamber no longer limits production.

They would also like to make hydrogen peroxide in higher concentrations. However, only a few milligrams are needed to treat one liter of water, and the current prototype already produces a sufficient concentration, which is one-tenth the concentration of the hydrogen peroxide that you buy at the store for your basic medical needs.

In the long term, the team wants to change the alkaline environment inside the cell to a neutral one that’s more like water. This would make it easier for people to use, because the hydrogen peroxide could be mixed with drinking water directly without having to neutralize it first.

The team members are excited about their results and feel they are on the right track to developing a practical device.

“Currently it’s just a prototype, but I personally think it will shine in the area of decentralized water purification for the developing world,” said Bill Chen. “It’s like a magic box. I hope it can become a reality.”

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