Next week’s night sky:
From Saturday onward, the night is prime milky-way viewing. Go out at around 2 hours after sunset to look at the beautiful band of bright stars snaking across the sky!
Martian Images
Images of knobbly rocks and rounded hills are delighting scientists as NASA’s Curiosity rover climbs Mount Sharp, a 5-mile-tall mountain within the 96-mile-wide basin of Mars’ Gale Crater. The rover’s Mast Camera, or Mastcam, highlights those features in a panorama captured on the 3,167th Martian day,.
This location is particularly exciting: Spacecraft orbiting Mars show that Curiosity is now somewhere between a region enriched with clay minerals and one dominated by salty minerals called sulfates. The mountain’s layers in this area may reveal how the ancient environment within Gale Crater dried up over time. Similar changes are seen across the planet, and studying this region up close has been a major long-term goal for the mission.
Sodium jets of an asteroid
The 3.6-mile-wide near-Earth asteroid Phaethon brightens as it nears the sun, passing well within the orbit of Mercury and heating up to some 750 C (1,390 F). Any water, carbon dioxide or carbon monoxide ice would have been baked out long ago, but the asteroid still brightens as it nears the Sun, much like a comet when sub-surface ice vaporizes.
A new study suggests the culprit may be sodium fizzing from Phaethon’s rocky surface into space. The conclusion is intriguing because it may help explain the annual Geminids meteor shower
Phaethon is a curious object that gets active as it approaches the Sun — researchers know it’s an asteroid and the source of the Geminids. But it contains little to no ice, so they were intrigued by the possibility that sodium, which is relatively plentiful in asteroids, could be the element driving this activity.
Repeated passes close to the Sun would have vaporised sodium on the surface, but interior deposits could still heat up and boil away into space through cracks and fissures in the asteroid’s crust. Those jets could provide the push needed to blow rocky debris off the surface and into space, explaining both the brightening of the asteroid and the Geminids meteor shower.
The results support the idea that categorising small bodies as either asteroids or comets is oversimplified. The distinction not only depends on the amount of ice present, but also on the presence of elements that vaporise at higher temperatures.
Said Masiero: “Our latest finding is that if the conditions are right, sodium may explain the nature of some active asteroids, making the spectrum between asteroids and comets even more complex than we previously realised.”
To learn more, go here: https://iopscience.iop.org/article/10.3847/PSJ/ac0d02