Explain Ceres?

Is Ceres gravity too high to allow a velocity-matched, orbit-following, sentinel "rock" to impact gracefully?

On Thu, 25 Jun 2015 22:27:19 -0700 (PDT), "Chris.B"
wrote:

Is Ceres gravity too high to allow a velocity-matched, orbit-following, sentinel "rock" to impact gracefully?

Not sure exactly what you're asking. What do you mean by "velocity
matched"?

The slowest ballistic impact velocity- that is, the slowest speed that
something can reach the surface by falling- is just Ceres's escape
velocity, 510 m/s. More than 1000 mph. Not a "graceful" impact.
(Earth's escape velocity is 11.2 km/s, which is why this is the
slowest speed a meteor can have).

If you could enter orbit first, the slowest possible impact speed
would be reduced to about 360 m/s. Still pretty fast.

On Friday, 26 June 2015 08:54:50 UTC+2, Chris L Peterson wrote:

Not sure exactly what you're asking. What do you mean by "velocity
matched"?

The slowest ballistic impact velocity- that is, the slowest speed that
something can reach the surface by falling- is just Ceres's escape
velocity, 510 m/s. More than 1000 mph. Not a "graceful" impact.
(Earth's escape velocity is 11.2 km/s, which is why this is the
slowest speed a meteor can have).

If you could enter orbit first, the slowest possible impact speed
would be reduced to about 360 m/s. Still pretty fast.

Thanks. I was just trying to trivialise the arrival of an external object on the surface over which so much fuss is being made. Given an external origin for the mountain being hyped as a "pyramid" requires that it does not penetrate so deeply, as to cause a noticeable crater. Nor for it to break up on impact.

Given your suggestions as to the minimum impact velocity, and general cratering providing a rough guide to Ceres' surface density, an external object is unlikely to have caused the [unlikely] "pyramid." Which, presumably, leaves only vulcanism, rather than plate tectonics, to cause a single mountain to form in a relatively flat plain.

Very large ants do seem unlikely given the scarcity of atmosphere. This also precludes intelligent builders unless they have robots.

On Friday, 26 June 2015 02:54:50 UTC-4, Chris L Peterson wrote:
On Thu, 25 Jun 2015 22:27:19 -0700 (PDT), "Chris.B"
wrote:

Is Ceres gravity too high to allow a velocity-matched, orbit-following, sentinel "rock" to impact gracefully?

Not sure exactly what you're asking. What do you mean by "velocity
matched"?

The slowest ballistic impact velocity- that is, the slowest speed that
something can reach the surface by falling- is just Ceres's escape
velocity, 510 m/s. More than 1000 mph. Not a "graceful" impact.
(Earth's escape velocity is 11.2 km/s, which is why this is the
slowest speed a meteor can have).

If you could enter orbit first, the slowest possible impact speed
would be reduced to about 360 m/s. Still pretty fast.

Terminal velocities to Earth are government by object shape, weight and primarily air-resistance, working against gravity. NOTHING falls to Earth at speeds beyond about 200mph when they impact the surface unless it has huge motive speed coming in and a large mass. Skydivers who have reached higher velocities have only done so very high up and speed diminishes as they get closer to the ground in the atmosphere.

On Friday, June 26, 2015 at 7:27:01 PM UTC-7, RichA wrote:
On Friday, 26 June 2015 02:54:50 UTC-4, Chris L Peterson wrote:
On Thu, 25 Jun 2015 22:27:19 -0700 (PDT), "Chris.B"
wrote:

Is Ceres gravity too high to allow a velocity-matched, orbit-following, sentinel "rock" to impact gracefully?

Not sure exactly what you're asking. What do you mean by "velocity
matched"?

The slowest ballistic impact velocity- that is, the slowest speed that
something can reach the surface by falling- is just Ceres's escape
velocity, 510 m/s. More than 1000 mph. Not a "graceful" impact.
(Earth's escape velocity is 11.2 km/s, which is why this is the
slowest speed a meteor can have).

If you could enter orbit first, the slowest possible impact speed
would be reduced to about 360 m/s. Still pretty fast.

Terminal velocities to Earth are government by object shape, weight and primarily air-resistance, working against gravity. NOTHING falls to Earth at speeds beyond about 200mph when they impact the surface unless it has huge motive speed coming in and a large mass. Skydivers who have reached higher velocities have only done so very high up and speed diminishes as they get closer to the ground in the atmosphere.

If I were to speculate that this 'pyramid' mountain was the rebound central peak of an ancient crater whose rim has been mostly eroded... what would be the arguments against that being the case? In the few pictures available of the area, I swear I can see parts of a rim of a large crater centered on the mountain... but then, such phantom rims are easy to see just about anywhere you care to look.

\Paul A

On Fri, 26 Jun 2015 19:26:59 -0700 (PDT), RichA
wrote:

Terminal velocities to Earth are government by object shape, weight and primarily air-resistance, working against gravity. NOTHING falls to Earth at speeds beyond about 200mph when they impact the surface unless it has huge motive speed coming in and a large mass.

Meteor velocities are typically specified as v-infinity, or the speed
when they first encounter the atmosphere. For long paths, the average
speed and final speed (where ablation ceases) are also interesting.

On Fri, 26 Jun 2015 19:45:23 -0700 (PDT), palsing
wrote:

If I were to speculate that this 'pyramid' mountain was the rebound central peak of an ancient crater whose rim has been mostly eroded... what would be the arguments against that being the case? In the few pictures available of the area, I swear I can see parts of a rim of a large crater centered on the mountain... but then, such phantom rims are easy to see just about anywhere you care to look.

Although we have little evidence, and little knowledge so far of the
material characteristics of Ceres, that would also be my first guess.
It's consistent with complex craters seen on other bodies.