Old Faithful has nothing on his on. Yellowstone may be impressive, but it turns out that Enceladus is covered with geysers. Enceladus, one of Saturn’s many moons, has a strange fractured surface, with large ‘tiger’ stripes running the width of the planet. We’ve long suspected that here stripes are fractures in the icy crust of the moon, but never suspected they would be the source of quite so much activity.
Then, back in 2005, we saw the first geysers on Enceladus. These were vast plumes of water ice stretching far above the surface of the moon, and led to the the new train of thought that these moons could harbor a liquid pool under the surface.
Now, we’ve got enough data to show that the geysers do in fact come directly from these fractures. Turns out these must be powered from deep down inside the moon. 101 geysers were viewed in total, and they each lie along one of the main 4 stripes. Discovery of the geysers has excited astrobiologists, who see water as a crucial ingredient for alien life. Next up has to be a lander to sample the geyser plumes.
Out of all the places in the solar system that NASA could look for ice, you would think that the planet closest to the Sun would be way down the list. It gets up to 450 degrees during the day, there is no atmosphere, no activity, nothing.
But Mercury ‘s tilt is almost directly up, I.e., it’s North Pole points directly up out of the solar system. It’s rotation is very slow, such that its year is 1 and a half ‘days’ (and its real solar day is actually 2 of its years) so it get baked on the dayside and cooled to -150 degrees on its night side. Put all this together and frozen water ice might survive. Especially at the poles.
Now, Nasa has confirmed this by capturing the first ever pictures of water ice on Mercury. It turns out that craters near the poles can be permanently shadowed from the Sun. Scientists have long thought this might be the case especially when radio telescopes scanning the planet found strongly reflected radar signals (a good sign that ice is present).
In this most recent study, scientists examined a number of impact craters near Mercury’s north pole and found that the deposits were made surprisingly recently. “The sharp boundaries indicate that the volatile deposits at Mercury’s poles are geologically young,” wrote the study’s authors in the journal Geology, “and either are restored at the surface through an ongoing process or were delivered to the planet recently.” Now we have definitely found ice on Mercury, we have to explain how it got there.
Like every discovery, it poses more questions.
Science is great. We think we have a problem solved, all the loose ends tied up, and then up pops a new discovery. Some see this as evidence of science’s fragility. Of course those people don’t understand the scientific method. In science, nothing is sacred, nothing is sacrosanct, everything is open to new data.
The latest episode to remind us of the power of the scientific method involves the Man on the Moon – the dark region known as Procellarum that is easily visible from Earth. As one of many Lunar Maria, we automatically thought it formed the same way as the other Maria – a late giant impact broke through the surface and cause lava to flow up, which then cooled as the dark material we see. But new data obtained by NASA’s GRAIL mission reveals that the Procellarum region likely arose not from a massive asteroid strike, but from a large plume of magma deep within the moon’s interior.
Scientists have created a map of the Procellarum, and found that its border is not circular, but polygonal, composed of sharp angles. These could not have been created by a massive asteroid. Instead, it is more likely that these were produced by giant tension cracks in the moon’s crust as it cooled around an upwelling plume of hot material from the deep interior. As cracks occurred, they formed a “plumbing system” in the moon’s crust through which magma could meander to the surface.
So it turns out that we were right about the lava flow part, but at least for this Maria, we were probably wrong about how the lava came up.