# The planet that could have been **URL:** \ **Category:** Factual Questions\ **Created:** [October 18, 2010, 6:07pm UTC](https://boards.straightdope.com/t/the-planet-that-could-have-been/557574 "2010-10-18T18:07:25Z")\ **Posts on this page:** 8\ **Page:** 1
**Author:** ![Rixlan](https://avatars.discourse-cdn.com/v4/letter/r/a183cd/32.png) [@Rixlan](https://boards.straightdope.com/u/Rixlan)\ **Post date:** [October 18, 2010, 6:07pm UTC](https://boards.straightdope.com/t/the-planet-that-could-have-been/557574/1 "2010-10-18T18:07:25Z")
I’ve heard it claimed that the asteroid belt is where a planet was prevented from forming due to Jupiter’s gravitational influence. I’ve always wondered, if all the mass in the asteroid belt was brought together how big a planet would it make? And what effect would this planet have on the rest of the solar system? ---
**Author:** ![Giles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giles/32/60_2.png) [@Giles](https://boards.straightdope.com/u/Giles)\ **Post date:** [October 18, 2010, 6:15pm UTC](https://boards.straightdope.com/t/the-planet-that-could-have-been/557574/2 "2010-10-18T18:15:05Z")
[The Wiki article](http://en.wikipedia.org/wiki/Asteroids) says, > [@](#): > > The mass of all the objects of the Main asteroid belt, lying between the orbits of Mars and Jupiter, is estimated to be about 3.0-3.6 × 10^21 kg, or about 4 percent of the mass of the Moon. Of this, Ceres comprises 0.95 × 10^21 kg, some 32 percent of the total. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [October 18, 2010, 6:17pm UTC](https://boards.straightdope.com/t/the-planet-that-could-have-been/557574/3 "2010-10-18T18:17:38Z")
Wiki: [Asteroid belt - Wikipedia](http://en.wikipedia.org/wiki/Asteroid_belt) > [@](#): > > The current asteroid belt is believed to contain only a small fraction of the mass of the primordial belt. Computer simulations suggest that the original asteroid belt may have contained mass equivalent to the Earth. Primarily because of gravitational perturbations, most of the material was ejected from the belt within about a million years of formation, leaving behind less than 0.1% of the original mass. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [October 20, 2010, 9:30am UTC](https://boards.straightdope.com/t/the-planet-that-could-have-been/557574/4 "2010-10-20T09:30:02Z")
Note that for the same reason (gavitational perturbation by Jupiter) Mars is much smaller than it would otherwise have been. ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [October 20, 2010, 10:01am UTC](https://boards.straightdope.com/t/the-planet-that-could-have-been/557574/5 "2010-10-20T10:01:46Z")
Fuckin’ Jupiter. ---
**Author:** ![Meurglys](https://avatars.discourse-cdn.com/v4/letter/m/258eb7/32.png) [@Meurglys](https://boards.straightdope.com/u/Meurglys)\ **Post date:** [October 20, 2010, 10:40am UTC](https://boards.straightdope.com/t/the-planet-that-could-have-been/557574/6 "2010-10-20T10:40:35Z")
I worked out a while ago that if all the material currently in the asteroid belt coalesced around Ceres, it would be around 900 miles across. Still pretty small - about 40% the diameter of the Moon. And I may well be completely wrong, as it was just idle curiousity when I played with the figures. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [October 20, 2010, 2:01pm UTC](https://boards.straightdope.com/t/the-planet-that-could-have-been/557574/7 "2010-10-20T14:01:02Z")
> [@Alessan](#): > > Fuckin’ Jupiter. To he who has much, much will be given. And from he who has little, much will be taken. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [October 23, 2010, 11:40am UTC](https://boards.straightdope.com/t/the-planet-that-could-have-been/557574/8 "2010-10-23T11:40:12Z")
Here’s something relevant I just saw: [Our “New, Improved” Solar System](http://www.skyandtelescope.com/community/skyblog/newsblog/105108519.html) Based on computer simulations, they’ve come up with a new idea on how the Solar System got to the way it is and it’s a scenario where the asteroid belt is not a failed planet. You can read that over for more details, but it goes roughly like this: Jupiter initially formed about 3 1/2 AU from the sun. Due to interactions with planitesimals, it migrated inward to about 1 1/2 AU. There it truncated the inner disk to about 1 AU. This inner disk, made of mostly rocky material, is where the inner planets, including Mars formed. Mars later migrated out of this inner disk. Jupiter was in a 3:2 resonance with Saturn, which pulled it inward as well. Eventually Saturn got big enough that it stopped the inward migration of both it and Jupiter and then caused a migration out to their current positions. The Asteroid Belt is basically left over remnants either kicked out of the inner disk by Mars or scattered inward by Jupiter as it migrated outward.