2019
May
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Karst lakes on Titan

One of Saturn’s moons, Titan, has a number of similarities to Earth: it has a dense atmosphere, mountains, and deserts, it rains, snows, and storms, with precipitation collecting in lakes and flowing in rivers into oceans. One of the differences is that it is much colder there, with temperatures around negative 180 °C. Therefore, methane and ethane, which are gases on Earth, play the role of terrestrial water on Titan; they form ice and even the sand grains in the deserts consist of frozen methane mixed with water ice.

Most of our knowledge about Titan’s hydrogeology originates from NASA’s Cassini probe and ESA’s Huygens Lander. Even though Cassini long ago went out in a blaze of glory in Saturn’s atmosphere, its data is still delivering new discoveries. In its last fly-by past Titan on April 22, 2017, the probe delivered especially interesting information on the small lakes of Titan’s western hemisphere.

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Airborne telescope detects helium hydride ion in space

The helium hydride ion HeH+ is a puzzle in and of itself. As a noble gas, helium does not easily bond with other elements. And in the early universe, the selection of elements was much smaller than it is today: the only elements were hydrogen (H), helium (He), and traces of lithium, and only in ionized form, that is, without electrons, which form the basis for chemical bonds. After the big bang, the universe had to cool down first, for a period of approximately 300,000 years, before chemistry could begin.

At a temperature of about 3700 degrees Celsius, the existing atom nuclei recombined with free electrons and thus created the first neutral atoms. According to current popular models, the process began with helium. Hydrogen was still ionized at that time, so helium atoms could combine with free protons to create helium hydride ions HeH+, which therefore became the first molecular compounds in the universe. Later, neutral hydrogen atoms began forming and these reacted with HeH+, creating molecular hydrogen and helium.

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Traces of life in a meteorite from Mars

ALH-77005 has already been through a lot. The lump of stone, which weighs around one pound, was ripped from the surface of Mars 178 million years ago by the impact of a bigger meteorite. The force of the impact flung it into space. Through no fault of its own, ALH-77005 was then put on a course to Earth, where it arrived three million years later.

It was bigger at the time, but its entry into the Earth’s thick atmosphere would have broken it apart. A lump of brown-gray stone, weighing 483 grams and measuring 9.5 cm x 7.5 cm x 5.25 cm, survived the descent and buried itself into Antarctic ice. There it remained for 175 million years until American and Japanese researchers discovered it in 1977.

Scientists quickly determined that ALH-77005 had come from Mars. To get at its real secrets, however, they had to cut it open. This provides an urgent lesson to any aliens out there whose outer appearance might be mistaken for that of a rock: don’t fall to Earth! A thin slice of the stone made its way to Hungary, where researchers put it under a microscope – and discovered some very exciting details that can now be read in a report.

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What dark matter is (not) made of

“When you have eliminated the impossible, whatever remains, however improbable, must be the truth,” the detective, Sherlock Holmes, says to Dr. Watson in “The Sign of the Four.” Cosmologists searching for dark matter, which should make up 85 percent of the universe’s mass, seem to be following a similar process right now. They are eliminating one component after another. Recently, they succeeded in eliminating two more possibilities.

Dark matter is not made up of tiny black holes. This result was shown by astronomers with the help of the Japanese Subaru telescope. Their strategy was very interesting. According to theories developed by, among others, Stephen Hawking, the universe might be full of tiny, micrometer-sized black holes created in the big bang. These primordial black holes are, of course, invisible. But their interactions can be detected due to their gravitation. If there were a large number of them between the Earth and the Andromeda Galaxy, they would have to continuously bend the light from stars in the distant galaxy. The astronomers looked for such bending – and they didn’t find it in an adequate amount, so these primordial black holes are no longer considered candidates for the missing dark matter.

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The weather for HR 8799 e: 1000 degrees Celsius with clouds of iron and silicate dust

HR 8799 e is a rather inhospitable place. The celestial body discovered in 2010 and orbiting the 30-million-year-young star HR 8799 at a distance of 129 light-years from Earth is a gas giant similar to Jupiter. But its host star shines nearly five times brighter than our Sun, creating a significantly hotter atmosphere for HR 8799’s innermost planet (despite the “e,” HR 8799 e is the closest planet to its host star) than Jupiter.

That is quite astonishing because at approximately 14.5 AU, HR 8799 e is almost five times farther from its host star than Jupiter is from our Sun. However, the gas giant also has five to ten times more mass and, because it is still rather young, like its star, has probably stored up a lot of heat from its birth phase. Astronomers at the European Southern Observatory (ESO) used the GRAVITY instrument on the Very Large Telescope Interferometer (VLTI) to make the first direct observation of an exoplanet by means of interferometry using HR 8799 e as the test subject.

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What does the interior of Neptune or Uranus look like?

Exploring the interior of icy giant planets is not an easy task. Without more advanced technology, we won’t be able to use probes to make measurements on site, so researchers must rely on models. These models are based on what scientists know about the substances that make up these ice giants such as Neptune and Uranus.

However, we can’t rule out that these models might contain errors. For example, it was previously assumed that carbon always took the form of diamond under very high pressures. Carbon and hydrogen are among the most abundant elements in the universe and make up a large portion of Neptune and Uranus, for example, in the form of methane. The deeper one goes down toward the center of either of these planets, the more extreme the conditions become. Initially, more complex structures of carbon and hydrogen are formed and then, at the very center, there is a solid core.

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How to send a spaceship to the closest star using lasers

The StarShot program wants to accelerate mini-spaceships by means of laser bombardment to a velocity of one-quarter the speed of light so that they can reach our neighboring star, Proxima Centauri, within the foreseeable future. The technology sounds feasible, but still must overcome a few hurdles.

Imagine you had to keep a ball floating in the air using a hairdryer. You will automatically think of a ping-pong ball floating a few inches above a fan. But could you accomplish this feat with a soccer ball located thirty feet above you? The hairdryer would have to be much larger and stronger.

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Is it possible to fly on Mars?

Of course, it’s possible to fly to Mars – but how about on Mars? The red planet’s atmosphere is significantly thinner than Earth’s. Atmospheric pressure at Mars’s surface is 0.00636 bar, which is one-hundred-fiftieth of the pressure at Earth’s surface. For a heavier-than-air aircraft to take off, it needs lift. It’s difficult to generate enough lift in such a thin atmosphere – but engineers at NASA’s JPL have apparently done it.

In any case, on NASA’s Mars 2020 rover mission, they want to include a small helicopter that could fly autonomously there at a height of up to five meters (sixteen feet). For comparison: this problem hasn’t been solved yet on Earth. The air pressure at Mars’s surface corresponds to the pressure in the Earth’s atmosphere at an altitude of 35 kilometers (22 miles) – and no helicopter has been able to fly that high yet.

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