It occurred to me that all my latest posts have absolutely nothing to do with space, so I figured I'd take a moment to show a few pictures that impress me. The irony isn't lost on me, however, that one of the two pictures you'll see here isn't from space.
I found this first picture on the "Astronomy Picture of the Day" website where I usually go when I want to see something new or interesting. The capture reads:
Volcano Tungurahua erupted spectacularly last year. Pictured above, molten rock so hot it glows visibly pours down the sides of the 5,000-meter high Tungurahua, while a cloud of dark ash is seen being ejected toward the left. Wispy white clouds flow around the lava-lit peak, while a star-lit sky shines in the distance. The above image was captured last year as ash fell around the adventurous photographer. Located in Ecuador, Tungurahua has become active roughly every 90 years since for the last 1,300 years. Volcano Tungurahua has started erupting again this year and continues erupting at a lower level even today.
This second picture is from my very own spacecraft that is orbiting Mars right now. The caption for this one reads:
False-color image of gully channels in a crater in the southern highlands of Mars, taken by the High Resolution Imaging Science Experiment (HiRISE) camera on the Mars Reconnaissance Orbiter. The gullies emanating from the rocky cliffs near the crater's rim (upper left) show meandering and braided patterns typical of water-carved channels. North is approximately up and illumination is from the left; scale, 26 centimeters per pixel.
Looking at this image, there seems little doubt that these structures were formed by a flowing fluid of some kind. Pictures like this look so very familiar, as if they were taken from a camera flying over a desert here on Earth. Yet these images are taken from Mars, where the geological and aeolian history is not well-understood.
Here on Earth, the forces that form the land are dominated by the motion of the tectonic plates and by erosion as the result of rainfall. Not so on Mars (at least not anymore), where the primary forces of change seem to be the wind, thermal cycles associated with seasons, and impacts from meteorites. Since this is our understanding, features like this are all the more perplexing (yet pleasing to see if we're ever to send people to Mars).
Nevertheless, there is plenty of evidence that Mars was once a much-wetter, much-warmer world where more Earth-like processes could have occurred. And there's still plenty of water there on Mars, it's just locked up in the soil, frozen at the poles.
So how did these channels form? Were they formed suddenly or over the course of millions of years? When? Were they formed by water or by something else? Why do we see these formations scattered across Mars, but not globally, like one would expect? How did the lower gravity on Mars (roughly 1/3 of Earth's) change how these look compared to how we'd see them on Earth?
So many questions.