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Gullies on Mars sculpted by dry ice rather than liquid water?

Mars’ gullies may be formed by dry ice processes rather than flowing liquid water, as previously thought. This is the conclusion of a study conducted by two French scientists published in Nature Geoscience. They show that, during Martian late winter and spring, underneath the seasonal CO2 ice layer heated by the Sun, intense gas fluxes can induce gas-lubricated debris flows which look like water-sculpted gullies on Earth.

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Einstein’s Cross under the gravitational microlens

A team of Spanish astrophysicists has obtained precise measurements for the innermost region of a disc of matter in orbital motion around a supermassive black hole in the lensed quasar known as Einstein’s Cross (Q2237-0305). It constitutes the most precise set of measurements achieved to date for such a small and distant object.

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Cassini completes final close flyby of Saturn’s moon Enceladus

NASA’s Cassini spacecraft has begun transmitting data and images from the mission’s 22nd and final close flyby of Saturn’s active moon Enceladus on Saturday, 19 December. Cassini has made so many breathtaking discoveries about this icy moon, its geologic activity and global ocean that lies beneath its icy crust, yet so much more remains to be done to determine if this tiny ocean world could harbour life.

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New findings on Pluto and its moons from New Horizons

Five months after NASA’s New Horizons spacecraft flew past Pluto, knowledge about this distant system continues to unfold, yet the spacecraft is less than halfway through transmitting data about the Pluto system to Earth. New Horizons science team members presented the latest findings at the American Geophysical Union (AGU) autumn meeting in San Francisco.

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How big can a black hole grow?

Black holes at the heart of galaxies could swell to 50 billion times the mass of the Sun before losing the discs of gas they rely on to sustain themselves, according to research conducted by Professor Andrew King from the University of Leicester’s Department of Physics and Astronomy.

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Did the ancient Egyptians record the period of eclipsing binary Algol?

A scholarly investigation of the Cairo Calendar papyrus (1244–1163 B.C.) has led researchers at the University of Helsinki to conclude that the ancient Egyptians were aware that the variable star Algol (beta Persei) had a 2.85-day period. Given that the star’s current period is 2.8673 days, this supports the theory that mass transfer between the stars of this eclipsing binary has caused a long-term increase of its orbital period.

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Asteroid looks even better second time around

Asteroid 1998 WT24 safely flew past Earth on 11 December at a distance of about 2.6 million miles (11 lunar distances). During its flyby, NASA scientists used the 230-foot (70-metre) DSS-14 antenna at Goldstone, California, to probe it with microwave transmissions. Using this technique, they created the highest-resolution radar pictures of the asteroid — 2.5 times better than when it was last imaged, 14 years ago.