New thinking about the shape of the ice shell on Enceladus raises the interesting possibility that the ocean believed to lie beneath is churning with currents. That would be a departure from the accepted view that the ocean -- thought to be 30 kilometers deep or more, as opposed to Earth's average of 3.6 kilometers -- is relatively homogenous. Remember, this is a body of water buried beneath perhaps 20 kilometers of ice, locked within a moon that is 500 kilometers in diameter. We know it's there because a 2014 flyby of the Cassini Saturn orbiter collected data on geyser activity erupting through the striking fissures in the south polar ice. That immediately put Enceladus high on the list of astrobiologically interesting targets along with, of course, Jupiter's moon Europa. Image: A masterpiece of deep time and wrenching gravity, the tortured surface of Saturn's moon Enceladus and its ongoing geologic activity tell the story of the ancient and present struggles of one tiny world. A...

The news that Ingenuity, the helicopter aboard NASA's Perseverance rover, contains a swathe of fabric from the 1903 Wright Flyer underscores the conflation in time I've been feeling all week, ever since looking at the images below. The first, released by the New Horizons mission team, shows a speck to the right of Pluto. This is 486958 Arrokoth, the Kuiper Belt Object visited by New Horizons at the beginning of 2019 and superimposed in the Pluto image just for scale. Image: The main exploration targets of New Horizons: Pluto (2015) and the much smaller Arrokoth (2019), to scale. Other exploration targets included Pluto's five moons. Credit: NASA/Johns Hopkins APL/Southwest Research Institute. The point is strikingly made: Pluto itself, which had been no more than a speck in our field of view in 1930, when what was deemed the ninth planet was discovered, has now become a world, and even the tiny Arrokoth is a well imaged object, the farthest ever visited by a spacecraft. Such...

Scientists at the European Southern Observatory are describing newly observed wind processes on Jupiter as "a unique meteorological beast." I like the phrase and can see its application to the 1450 kilometer per hour jets they've uncovered near Jupiter's poles. Just how they made this detection is fascinating in its own right, since they drew on a spectacular natural event, the 1994 collision of comet Shoemaker-Levy 9 with the planet, to deduce current conditions. The molecules that were produced in that impact are the lever that moves the investigation, which is headed by Thibault Cavalié (Laboratoire d'Astrophysique de Bordeaux). Image: This image shows an artist's impression of winds in Jupiter's stratosphere near the planet's south pole, with the blue lines representing wind speeds. These lines are superimposed on a real image of Jupiter, taken by the JunoCam imager aboard NASA's Juno spacecraft. Jupiter's famous bands of clouds are located in the lower atmosphere, where...

The orbital interactions between objects in a stellar system result in all kinds of interesting effects, a celestial pinball machine that sometimes flings planets outward to wander alone among the stars. Gas giants can be pulled from more distant orbits into a broiling proximity to their star. But the object known as P/2019 LD2 has a special interest because its interactions are happening in a tight time frame even as we observe them. We could call P/2019 LD2 a 'comet-like object,' because it sometimes acts like an asteroid, sometimes like a comet. It is in fact a Centaur, one of that group of outer system objects that only become active as they move into the inner system. We're watching a transition from Centaur to Jupiter family comet mediated by the gradually warming environment. This one evidently swung close to Jupiter roughly two years ago, to be flung by the giant planet's gravity toward the Trojan asteroid group that leads Jupiter in its orbit by some 700 million kilometers....

I can remember when I first read about the experiment that Stanley Miller and Harold Urey performed at the University of Chicago in 1952 to see if organic molecules could be produced under conditions like those of the early Earth. It was a test of abiogenesis, though that wasn't a word I knew at the time. Somewhere around 5th grade, I was a kid reading a book whose title has long escaped me, but the thought that scientists could re-create the atmosphere the way it was billions of years ago seized my imagination. Never mind that exactly what was in that atmosphere has been controversial. What thrilled me was the attempt to reproduce something long gone -- billions of years gone -- and to experiment to find out what it might produce. I just finished Samanth Subramanian's elegant biography of J. B. S. Haldane, the polymathic geneticist, mathematician, physiologist (and too much more to list here), whose work on the chemical formation of life was strongly supported by the Miller and Urey...