(Wait. What? You say you're not yet shopped out? Then see "Buy-a-Book Saturday redux." No need to be too literal here.)
Let's start with "An interstellar rock gets a name." The very first known interstellar interloper will henceforth be known -- never mind that it will soon have receded forever beyond our sight -- as Oumuamua. ("This is a Hawaiian name, meaning, roughly, 'very first scout.' ") Or, more formally, as 1I/2017 U1.
Oumuamua (an artists' conception) |
We've even gained an inkling about the appearance of Oumuamua. See "ESO Observations Show First Interstellar Asteroid is Like Nothing Seen Before: VLT reveals dark, reddish and highly-elongated object." (ESO is the European Southern Observatory. VLT is ESO's Very Large Telescope.)
You've likely encountered reports that surface flows of water have been detected on Mars. Not so fast. Once geologists from the US Geological Survey reviewed the satellite observations, they reached a different conclusion: that "The case for flowing water on Mars is drying up." More specifically, the geologists interpreted:
... the “streaks” didn't behave like flowing water. For one thing, they existed only at the tops of very steep slopes. For another, the streaks all seemed to end when their slopes matched the dynamic “angle of repose” — the steepest angle at which a given material can be piled without slumping.
If you've ever tried to build a sand castle, you're familiar with this concept. It's why dry sand -- which has a very shallow angle of repose -- tends to slide out of shape, but wet sand -- with a steeper angle of repose -- can be piled into towers and turrets.