"The Saturn was the second console designed during SEGA's "Planet Projects." The other two consoles designed were the SEGA Jupiter which became the 32X and the SEGA Neptune which was canceled before any working prototypes were finished. "
"History
[edit] Development
The Sega 32X allows the user to play 32-bit games on the Mega Drive, such as Doom
On January 8, 1994, Hayao Nakayama, then CEO of Sega, ordered his company to make a 32-bit cartridge based console that would be in stores by Christmas 1994. This would at first be named "Project Jupiter", but after Sega found CD technology cheaper, they decided to modify it instead of dropping the cartridge project (that would be called "Project Saturn"). Hideki Sato and some other Sega of Japan engineers came over to collaborate about the project with Sega of America's Joe Miller. The first idea was a new Mega Drive/Genesis with more colors and a 32-bit processor. And so, this project was codenamed Project Mars, and Sega of America was going to shape the project.
The 32X was primarily envisioned as a system which would extend the life of the Sega Mega Drive/Genesis and provide revenue while the installed userbase of the Sega Saturn slowly grew."
This article makes it seem Jupiter, Neptune and 32x (Mars) were BASICALLY, SORT OF, IN A WAY, the same thing. Different ideas though, Jupiter was supposed be enhanced standalone system (like Neptune EXCEPT maybe not backwards compatible with genesis, that is why Neptune seemed so kool at time) while Mars was as a add on and released as 32x. Which was both a good and bad idea.
The non cartridge 32 bit version became the Saturn.
The cartridge 32 bit ones was were Jupiter (cartidrige Saturn like 32x), then Mars (32x) was released as a add on but Neptune (genesis + 32x) was canceled after Mars (32x). They should have just released it. But so many people found out how to make their own, it's actually very easy.
http://en.wikipedia.org/wiki/Sega_32X
So the cdx is the Pluto I guess, j/k LOL, oh no that was Game Gear, no no no I got it it was the Nomad LOL. (Don't explain what the cdx, gg, nomad was was please, I had 2 of each for over a decade and loved the cdx, in fact I was one of first people to tell people online the 32x and power base DOES WORK in cdx.) IMO the cdx was so much better as a design than jvc wondermega.
Check this out proof of Saturn Cart/CD prototypes :


"Jupiter was a project which used the same components than Saturn, but using cartdridges instead of discs to store games. It's believed that the decision of using a CD-Rom unit was taken after the first presentation of Play Station...
Whatever which were the reason, Jupiter could be defined as a Saturn without CD-Rom unit (and some minor hardware changes) There're also more projects like Pluto or Eclipse, but they're just experiments from the past.
The Jupiter was SOA's counterpart to the Saturn project. It was intended to be a 32 bit cartridge based system. After Sega found CD technology to be cheaper, they decided to modify the Jupiter instead of scrapping it. SOA's Joe Miller felt gamers wouldn't buy an improved version of the Megadrive, so it was decided to make the new project an add on to the Megadrive instead of an entirely new console. This became the 32X and was code named Mars. At this time, SOA was unaware of the Saturn project until Project Mars was well underway."
This post describes the "genesis" (pun intended) of Sega shooting themselves in foot. Spread out way too thin with all these released and unreleased machines. Then releasing Saturn early with not a great 3d chip but great 2d chip, non complete launch VF game then having to release a VF Remix to make up for their own mess up, no released 32x or saturn (esp !) sonic staring game...made it all go down hill faster and faster until dc revived them for a little bit, but the damage they done and ps2 announcement and no dvd player in dc (who cares now about that LOL) doomed them. Everyone was right, Sega did it to themselves.
I remember being such a Sega fan and ignorant to all this info I was telling others "Your just a Sega hater ! The Genesis, sega cd, 32x, saturn were cool systems" but after reading how stupid Sega management handled the overuse of projects and not communicating with each other etc, and how spread out they became with sega products or licenses, it's clear Sega definitely killed themselves more than anybody killed them in hardware market.