The process of writing posts for TYWKIWDBI keeps driving me to various corners of the internet, where I encounter things that I not only didn't know, but couldn't even imagine. As a child I was told that one of the special features of our planet was the availability of abundant water. Later I came to understand via reading (and movies) that there are extraterrestrial "water worlds," including within our own solar system (Europa has more water than Earth does).
In 2009 I blogged Surprising quantities of water on the moon!, adding the exclamation point to the title. Earlier this year it was Huge quantities of water ice detected on Mars, without the exclamation point because earlier studies of Mars geology had suggested that the planet had once had abundant water.
None of that previous knowledge prepared me for the shock of reading recently that NASA has found good evidence for water ice on the planet Mercury.
"The yellow regions in many of the craters mark locations that show evidence for water ice, as detected by Earth-based radar observations from Arecibo Observatory in Puerto Rico. MESSENGER has collected compelling new evidence that the deposits are indeed water ice, including imaging within the permanently shaded interiors of some of the craters, such as Prokofiev and Fuller."
I have embedded above an hour-long video from the NASA channel presenting the recent conference summary. Knowing that most of the readers of TYWKIWDBI fall into the TLDR category, here is my oversimplification.
It begins with the realization that although Mercury as a whole is incomprehensibly hot, it is not uniformly hellish. This scan of a polar region shows temperatures ranging from 50 degrees Kelvin (-223 Celsius, -369 Fahrenehit) to 500 degrees Kelvin (227 Celsius, 440 Fahrenheit). The temperature at which water freezes would be the 273K yellow shade. The blues below that are subfreezing.
Point #2 is that some areas in craters are in permanent shadow from incident light:
Water would arrive via the impact of icy comets or meteors -
The non-water dust/rocks in the impacts would provide a modicum of cover for the ice, delaying its sublimation.
Recent instrumentation has shown the depth of water ice in these craters
I just speeded through the video myself while taking the screencaps, so I need to go back and listen in detail for the nuances. (on second speed-through I heard comment that liquid water is still impossible on Mercury because the absence of an atmosphere would result in only meta-stable liquid form that would immediately volatilize.)
I'm just totally gobsmacked, especially by the cosmic implication that all this water is flying all around the universe and crashing into planets that have moderate temperatures, and that this has been going on for billions of years (see early universe link below), which raises in my estimation the likelihood of water-based life elsewhere in the universe close to certainty.
You learn something every day.
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