Outer Solar System

Looking for Our Sun’s ‘Super-Earth’

March 27, 2017

An obscure instrument called a blink comparator became world famous following Clyde Tombaugh’s discovery of Pluto in 1930. It was by rapidly switching between astronomical photographs that the young Tombaugh was able to compare objects in the field of view where ‘Planet X’ was presumed to hide. Pluto turned out to be a good deal […]

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Ceres: Axial Tilt and Surface Ice

March 23, 2017

Earth’s axial tilt (its obliquity) is 23.5 degrees, a significant fact for those of us who enjoy seasonal change. The ‘tilt’ is the angle between our planet’s rotational axis and its orbital axis. If we look at Earth’s obliquity over time, we find a 41,000 year cycle that oscillates between 22.1 and 24.5 degrees. Here […]

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Titan: Nitrogen Bubbles and ‘Magic Islands’

March 16, 2017

With Cassini now in the final stages of its mission, we can look forward to just one more close flyby of Titan, the 127th targeted encounter, on April 22. ‘Targeted’ means that Cassini has to use its thrusters to position itself optimally for the flyby. The first of the images below, by contrast, comes from […]

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Ceres: Close Look at Occator Crater

March 7, 2017

We’ve looked recently at the possibility of cryovolcanism on Ceres with regard to the unusual feature called Ahuna Mons (see Ice Volcanoes on Ceres?). Now we have further evidence that outbursts of brine from beneath the surface have been occurring over long periods of time, and that some of these eruptions have been recent. The […]

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Fragmented Asteroid Develops Comet-like Tails

March 6, 2017

You wouldn’t expect main belt asteroids to develop tails like comets — their orbits are circular enough that they don’t undergo the kind of temperature swings many comets experience in their plunge toward perihelion — but we do have some twenty cases of asteroids that do exactly that. The photo below, showing imagery from the […]

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NASA Report on Europa Lander

February 13, 2017

With an ocean containing twice as much water as Earth’s oceans, Europa is a high-priority target for astrobiology. But the presence of water alone is not what gives the Jovian moon such interest. After all, we’re learning that icy worlds beyond the snowline can feature oceans beneath the surface, and we’re learning more all the […]

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Cassini: Grazing the Rings

February 8, 2017

I don’t want to get much deeper into February without looking at the recent Cassini imagery from Saturn’s rings. Cassini, after all, is a precious resource, and every day that passes brings us closer to its mission-ending plunge into Saturn’s cloud tops this September. Leading into that climactic event, however, we have the current ring-grazing […]

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Ice Volcanoes on Ceres?

February 7, 2017

If a terrestrial volcano erupts in molten rock, an ice volcano in the outer Solar System would presumably erupt with volatiles like water or ammonia. We have evidence of such things in places like Pluto and Triton, far beyond the snowline where water is abundant. Some scientists think Quaoar may have had cryovolcanic activity, and […]

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PROCYON: An Overview of Cometary Water

January 25, 2017

The Japanese PROCYON spacecraft (Proximate Object Close flyby with Optical Navigation) has just given us an interesting case of repurposing a scientific instrument, not to mention drawing value out of a mission whose initial plans had gone awry. Launched together with JAXA’s Hayabusa 2 probe in late December of 2014, PROCYON was to have flown […]

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Probing the Surface of Ceres

January 24, 2017

It doesn’t stretch credulity to hypothesize that the early Earth benefited from an influx of comet and asteroid material that contributed water and organic compounds to its composition. The surface of a world can clearly be affected by materials from other bodies in the Solar System. Now we’re learning that the dwarf planet Ceres may […]

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