Well, if Mars replaces the Moon, the month will be only 26 days long and the tides will be 8.7 times higher. For example, there will 40 foot tides in NYC. Also...
2/ Only 6 ancient planets will be visible (the Greeks counted the Sun and Moon as planets making 7) so when the Roman Empire adopts the Jewish 7 day week, it won’t fit the (now-) 6 day Hellenistic horoscope system, so we won’t end up with a day called Saturday (or even Jaturday)
3/ So there won’t be a webcomic by @ZachWeiner called Jaturday Morning Breakfast Cereal. (Sorry Zach.😢) Maybe Saturday Night Live @nbcsnl can be renamed Super Earth Night Live? 🤷♂️
4/ Herschel won’t discover Uranus (Neptune is a bit too far for his telescope). He won’t become famous and meet his wife. John Herschel inventor of the blueprint is never born. The world ends up using purpleprint technology instead. The @usedgov writes “A Purpleprint for Reform.” 
5/ The interminable argument between Moon people and Mars people over which place NASA should explore is still interminable, but now it is an argument between Mars people and Super Earth people. For a while, NASA has the slogan #JourneyToSuperEarth.
6/ The SuperEarth people will actually win that argument because the nearby Mars will be far less interesting as a destination than Mars is today. That’s because it won’t have polar caps, atmosphere, or evidence of ancient water. (More on that, below.)
7/ Also, the people who live on Earth won’t be humans, it turns out. They were settled here by an advanced alien species because this solar system had no civilization of its own. They said, “here’s a good place to resettle these primitives whose star was wrecked by a black hole.”
8/ The reason this solar system produced no civilization is because it didn’t have both a Jupiter and Saturn. Without both, they can’t get into 2-to-1 orbital resonance, so they couldn’t kick Neptune into the Kuiper Belt which sent hordes of comets into the inner solar system.
9/ Without the bombardment of icy bodies, Earth would have no oceans and little carbon, so it would have no advanced life, if any life at all. Likewise Mars would not get an early ocean. So no Martian clay, no river systems, no possible life, etc. Much more like the actual Moon.
10/ And since it is now so much closer to the sun, but still quite small, it will be hotter and lose its atmosphere faster and more completely. It will still end up as an airless body. Just like the Moon, only bigger. 🤷♂️
11/ Part of the Moon’s beauty is that it is so small so we can affordably launch water ice off its surface to use as rocket fuel. But the size of Mars, it will be far less economical to launch resources from its surface. Goodbye, cislunar (or cis-Martian) economy. 😭😭😭
12/ So the SuperEarth camp will win. It’s #JourneyToSuperEarth for NASA! But the PRESSURE on Super Earth: how do we explore it?! Well, the astronauts orbit it and teleoporate robots on the surface. Later we use these things. No space suits. (Credit: Customs House Museum)
13/ The non-humans live on Earth because the advanced species terraformed Earth before settling them here. They artificially transported icy bodies to create oceans, seeded life at a high rate using mega incubators, and plopped the ancient people down.(Karen Carr/Smithsonian)
14/ When they developed technology and started exploring space, nothing made any sense. The solar system clearly did not have a history that explained the conditions for life on Earth. Some of them began to suspect it was the aliens. It actually was the aliens. 🙃😉
15/ Those mystery planets between Mercury and the Sun: I know what they’re named! In 2002, @AlanStern & Dan Durda of @SwRI flew fighter jets looking for these “vulcanoids”. In our timeline they didn’t find them. But in this alternate solar system they DID! nasa.gov/centers/dryden…
16/ So these three small planets are named Stern, Durda, and Verrier.(Verrier studied their possible existence in the 1850s.) For Verrier this discovery is a great consolation, because without Uranus he was unable to discover Neptune. So that’s good news!
17/ Another funny thing is how Pluto and Triton got captured by Neptune. As mentioned above, without separate Jupiter & Saturn, the dynamics don’t cause Neptune to plow into the Kuiper Belt, sweeping Kuiper Belt Objects into resonance with itself and capturing Triton as a moon.
18/ Not only is Triton a moon, so is Pluto. TWO “dwarf planets” captured to become “secondary planets”. (That’s what Kepler called them.) Does this actually resolve the question about Pluto’s planethood? I mean, it’s still a planet either way. (You’re not getting off that easy😘)
19/ Planetary scientists call large moons “planets”. This has been the case since time immemorial. Copernicus, Galileo, Kepler, every astronomy textbook until the 1920s: they formally classified large moons as planets. Modern astronomers and some planetary scientists forgot.
20/ One last weird thing: the rings of Venus. How does Venus hang onto rings so close to the sun? I’m just going to guess that a collision created Venus’ rings very recently, so they’re still there. Venus used to have three moons but two collided so now it has only two. 🤷♂️
21/ But if it had three moons — count them, THREE — then how did it get them? 😉🙃 Well maybe they accreted in orbit after a giant collision with Venus’ surface? Like what we think may have happened when Earth’s (actual) Moon formed?
22/ So that explains what happened to Theia! Now it makes sense. In our actual solar system Theia is what we think collided with Earth leading to formation of the Moon. But in this solar system it happened (at a later date, apparently) to Venus! And the debris is still accreting!
23/23 So I have to say I like our solar system the way it is... except maybe adding the vulcanoids Stern, Durda, and Verrier inside the orbit of Mercury. Those are pretty awesome, and probably wouldn’t mess up everything else. But who knows? We still have so much to learn.
