Many Moons, tidally locked, are in prograde orbits about planets in prograde movement around the Sun. The result is that during Lunar aphelia, the orbital velocities of parent body and satellite are added., when closer to the Sun, subtracted, working in opposite directions. Case in Point: Europa. Orbital velocity about Jupiter: 13.74 km/sec. Vo Jupiter system about Sun 13.07 km/sec. so, it appears when aligned at perihelion, Europa should move backward on it's orbit around the Sun, and to get to that point has to come to a standstill. In a cycloid motion akin to a Rail road wheel, with a flange that moves backward from the train travel near the ground. Therefore, As seen on the far side Europa, near mid - month, the Sun must stand still and reverse in the sky for a while. Would that not create a hot spot, that would get a repeat heat treatment next time around every 84 hours? The area opposite that tropical spot, facing Jupiter all the time. would it not travel at ~22 km/sec around the Sun at aphelion? Have less chance to dwell and absorb heat the same band of solar radiation where the antipode saw the Sun loop, linger in the sky.What are the results of such thermal tides? and What effect does hanging nearly motionless with respect to the Sun at perihelion and doubling your orbital speed at aphelion have on the shape of your orbit around both the Sun? and Jupiter?
"A runner or moon that has to backtrack must have to take longer time." *explained in Another thought experiment here, reading time 3 minutes. Assuming an observation station on the Jupiter orbit, fixed under the stars, has Jupiter and Europa zipping by. Jupiter leading. A spot on the apparent center of Europa is tagged. Using the Doppler effect, looking at the receding pair, since momentarily both are in line, and the Sun is to the left, Europa a half moon, both bodies clock in as moving away at 13.07 km/sec. 21 hours, later, with Europa, and the spot to the right, still a half moon, (or in Jupiter's shadow) and Europa at aphelion, Europa is measured as moving away 13.74 km/s faster than Jupiter, more than twice as fast, 26.8 km/sec. seemingly in a hurry to get that spot out of that cold place. Then, another "week" later, (halfway) when Europa is leading Jupiter on orbit direction, both are again moving away with the same shared velocity of 13.07. km/se. But Another 1/4 turn later, when Europa has moved to the left, and is at it's Perihelion, the radar registers something strange, Europa and the tag appear to have actually changed direction, approaching the fixed observer at 670 meter per second. , after obviously having to come to a momentary standstill. As if the spot wanted to linger in that direct sunshine as long as possible!! Before returning to the starting line up, another standstill will have to be measured, as Europa returns to its initial line up and shared "receding" speed. The tagged spot now seeing sundown again. Now, Imagine another spot is tagged, at (halfway), when Europa is positioned far, ahead and leading Jupiter on orbit. This different marker, on the opposite side of Europa, would, when now moving left to perihelion, linger in it's night shadow, although being bathed in "Jupiter shine" at that time, At aphelion, it would hurry through the sunshine phase at 23+ km/see. . Keeping cool a long time, hurrying through the heat. repeat and repeat, repeat, --once a month, every 84 hours, always the same spot. spot on? * unless she is allowed super speed on the back leg.
New Scientist: By Leah Crane "Titan has a huge ice belt near its equator, and we don’t know how it got there.--". and: from Science Daily Please Register or Log in to view the hidden image! This figure shows 3 orientations of Titan's globe. Mapped in blue is the icy corridor. " Yet the major ice feature the researchers found was completely unexpected. It consists of a linear ice corridor that wraps around 40 percent of Titan's circumference. University of Arizona. "Ice feature on Saturn's giant moon, TItan." ScienceDaily. ScienceDaily, 29 April 2019. <www.sciencedaily.com/releases/2019/04/190429111826.htm>. Not saying that this feature is caused by the difference in perihelion and aphelion exposure to solar energy, but here it is: one sided feature, perhaps temperature dependant. Sidereal velocity of Titan at perihelion midday, 4.11 km/sec. on its opposite side, the one facing Saturn, at aphelion, 15.25 km/sec. ~ 4 times faster.
