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View Full Version : Is Ceres more massive than the rest of the asteroid belt combined?



parallaxicality
2005-Dec-31, 11:12 AM
Just wondering

Romanus
2005-Dec-31, 11:54 AM
Definitely not, though its mass probably makes up a significant fraction of the Belt's total mass.

Eroica
2005-Dec-31, 12:03 PM
No, but the Moon is bigger than all the asteroids combined. Two wikipedia articles seem to disagree on how much of the asteroidal mass is in Ceres:

Ceres (http://en.wikipedia.org/wiki/Ceres_%28asteroid%29)

[Ceres] is over half as massive as the rest of the belt put together.

Asteroid (http://en.wikipedia.org/wiki/Asteroid)

The mass of all the asteroids of the Main Belt is estimated to be about 2.3x1021 kg, or about 3% of the mass of our moon. Of this, 1 Ceres comprises 940 to 950x1018 kg, some 40% of the total.

Tim Thompson
2005-Dec-31, 05:22 PM
See the Asteroid Fact Sheet (http://nssdc.gsfc.nasa.gov/planetary/factsheet/asteroidfact.html) from the National Space Science Data Center (http://nssdc.gsfc.nasa.gov/) (NSSDC), Lunar and Planetary Science Section (http://nssdc.gsfc.nasa.gov/planetary/planetary_home.html).

1 Ceres - The largest and first discovered asteroid, by G. Piazzi on January 1, 1801. Ceres comprises over one-third the 2.3 x 1021 kg estimated total mass of all the asteroids.
In the fact sheet, the mass of Ceres is given as 8.70 x 1020 kg. Pallas weighs in at 3.18 x 1020 kg, and Vesta is good for 3.00 x 1020 kg. Together they amount to 1.49 x 1021 kg, or about 65% of the total asteroid mass. The mass of the moon, 7.35 x 1022 kg (Moon fact sheet (http://nssdc.gsfc.nasa.gov/planetary/factsheet/moonfact.html)) is 32 times greater than the mass of all the asteroids together.

And remember that this is all comparing to the asteroids that are roaming around with the planets, and in the asteroid belt (http://www.solstation.com/stars/asteroid.htm), but does not include the Kuiper belt (http://www.ifa.hawaii.edu/faculty/jewitt/kb.html) (or Edgeworth-Kuiper belt, if that makes you feel better). We now know that the largest Kuiper belt object (http://www.gps.caltech.edu/~mbrown/planetlila/index.html) is likely larger than Pluto (http://www.nineplanets.org/pluto.html).

Eroica
2005-Dec-31, 07:43 PM
I just realized that the two wikipedia articles I referenced are not at variance. Ceres does comprise about 40% (actually about 37.8%, using Tim's figures) of the asteroid belt, and so it is more than half as massive as the rest of the belt put together (40% being greater than 30%)! :wall:

I stand corrected.

Denis12
2005-Dec-31, 09:12 PM
And what about a mission to ceres? How will that go?

archman
2005-Dec-31, 10:46 PM
No, but the Moon is bigger than all the asteroids combined.

Dang, it's that much difference? So that old theory about the Belt being an "almost-planet" would have us thinking of some rinky-dink thing? I always thought there was enough mass for something on the order of the size of Mars. Oh well... I've learned my disappointing factoid for the day.

At least Han Solo won't have any trouble navigating our Belt, should he be chased by the Imperial Fleet.

the_shaggy_one
2005-Dec-31, 10:59 PM
Dang, it's that much difference? So that old theory about the Belt being an "almost-planet" would have us thinking of some rinky-dink thing? I always thought there was enough mass for something on the order of the size of Mars. Oh well... I've learned my disappointing factoid for the day.

At least Han Solo won't have any trouble navigating our Belt, should he be chased by the Imperial Fleet.

There might have been enough mass to form an earth or mars-sized body out there 4.5 billion years ago, but a lot of it got tossed out of area by jupiter pretty early on, so most of that mass went to jupiter, the sun, and the other planets instead. A lot of the asteroids out there are the partially-differentiated remains of several large planetoids that were obliterated billions of years ago.

Tim Thompson
2006-Jan-01, 06:17 PM
And what about a mission to ceres? How will that go?
I don't know anything about a mission specifically targeting Ceres. There are a few comet missions. Rosatta (http://www.esa.int/esaMI/Rosetta/index.html), an ESA mission, is on its way towards comet 67P/Churyumov-Gerasimenko (http://cometography.com/pcomets/067p.html), where it will become the first comet orbiter. Stardust (http://www.jpl.nasa.gov/missions/current/stardust.html) returns to Earth on January 15, with samples of dust from the tail of comet 81P/Wild-2 (http://cometography.com/pcomets/081p.html), and a sample of interplanetary & interstellar dust. The only asteroid specific mission I know of is the Japanese Hayabusa (http://www.isas.jaxa.jp/e/enterp/missions/hayabusa/index.shtml) (formerly known as Muses-C), which has, I think, already been to & left from, asteroid 25143 Itokawa (http://en.wikipedia.org/wiki/25143_Itokawa) (1998SF36). It will bring an asteroid sample back to Earth.

bigbluestar
2006-Jan-01, 06:30 PM
Dang, it's that much difference? So that old theory about the Belt being an "almost-planet" would have us thinking of some rinky-dink thing? I always thought there was enough mass for something on the order of the size of Mars. Oh well... I've learned my disappointing factoid for the day.
.

LOL you wanted something exotic huh. Well thats nature for you.......

parallaxicality
2006-Jan-01, 07:44 PM
And what about a mission to ceres? How will that go?
The "Dawn" mission (http://www.space.com/missionlaunches/051107_dawn_qown.html)