The planet Mercury, as imaged by the MESSENGER spacecraft [Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington]
More theoretical speculations about Mercury’s origins, arising from what is now believed to be evidence of historical volcanic activity.
Mercury is the closest planet to the sun, but far from being a dull cinder of a world, it has instead turned out to be a real eye opener for geologists, says Phys.org.
Among the revelations by NASA’s MESSENGER probe, which first flew past Mercury in 2008 and orbited it between 2011 and 2015, is the discovery of a hundred or so bright red spots scattered across the globe. Now they are at last being named.
Although they appear more yellow-orange than red on the accompanying colour-enhanced images, they are the reddest features on Mercury, a planet that looks dull and grey on unenhanced images.
Most have 10-50km wide irregularly-shaped holes at their centres. Scientists soon interpreted the holes as volcanic vents and the spots as material thrown out by volcanic explosions. Explosive volcanism was not expected at Mercury, because formation of a planet close to the heat of the sun should have deprived it of the gaseous content necessary to power explosions.
But MESSENGER revealed multiple lines of evidence showing that Mercury is actually quite rich in so-called “volatile components”. These include direct measurements of abundant sulphur, carbon, potassium and chlorine, and the discovery of patches of shallow hollows where it looks as if some unknown volatile material near the ground surface has been somehow dissipated into space.
Maybe this means that Mercury is actually the remains of an interloper from somewhere beyond the Earth’s orbit, where volatile material was available in greater amounts during planet formation. A “hit and run” impact with the Earth or Venus in the early stages of their formation while Mercury was migrating inwards towards its present orbit close to the sun could have stripped it of much of its original rock, leaving the dense but volatile-rich body we see today.
Compound vents
Whatever Mercury’s origin, the red spots and their source vents demonstrate explosive volcanic activity that in some cases likely continued into the most recent billion years of Mercury’s 4.5 billion year history. Scientists deduce this because some of the vents puncture young lava flows or the floors of young impact craters.
Overlapping structures within some vents show that they result from a succession of explosions at sites several kilometres apart. From this it can be inferred that each red spot is the accumulated product of several eruptions from its vent.
Continued here.
Tallbloke's Talkshop 
And how long before some alarmist claims that red spots are a sure sign of Climate Change?
Maybe this means that Mercury is actually the remains of an interloper from somewhere beyond the Earth’s orbit
Or maybe they’ve been watching too much sci-fi 😎
Venus turns the opposite way to other planets and also slowly. It is likely something collided with it
Venus rotates slowly in the wrong direction and has a MUCH too dense atmosphere to have originated in it’s present position. An amateur astronomer and writer, Immanual Velikovsky pointed these things out in 1948, a generation before the space programs discovered them to be true. Based on his studies of Ancient writings and astrophysics he speculated that Venus was a satellite of Saturn dislodged by some event and entered the inter system by way of a pass near Jupiter. There is no indication of a collision as Venus has no satellites or debris orbiting it. I remember when Venus was considered to be a twin of Earth. Venus is nothing like Earth!
As to Mercury and it’s spots ? ? ? Well it does rotate in the correct direction, slowly, so not quite tidally locked to the Sun. Small enough to be nearly core dead but tidal stirrings could cause shallow heating. Immanual Velikovsky claimed that Mercury and Mars were of the original creation while Earth/Luna and Venus were creations of later events. He also correctly described Titan.
I don’t know what kind of crystal ball Immanual Velikovsky used to determine these things but modern research and the space program has prove them correct. If you want to learn the truth about the creation of the U.S.S.R. and Israel, read his chronicles of those events. He lived them. There are also writings of his visits with Albert Einstein…pg