Asteroid - Mars non-impact question

Most recent estimate is that the probability of impact of 2007 WD5 with
mars is about 4%.

If it does not hit, it might be really close; what are the chances that its
orbit would be greatly changed?

Impact velocity is estimated to be (if occuring) 13.5 x10^3 m/s. Is it
possible that it could become a third martian moon(let)?

_ wrote:

Most recent estimate is that the probability of impact of 2007 WD5 with
mars is about 4%.

If it does not hit, it might be really close; what are the chances that its
orbit would be greatly changed?

Impact velocity is estimated to be (if occuring) 13.5 x10^3 m/s. Is it
possible that it could become a third martian moon(let)?

I would say that given all the uncertainties still involved it would
be best to wait until 1 February 2008 for the answer! The uncertainty
region is 400000 km by 600 km.

Assuming Mars is at one end and the asteroid at the other that would
be a fair miss. Given todays elements and assuming no perturbations
it looks like it will probably miss by about 180000 km. I doubt that
would be close enough to be captured - but why not wait and see!


Eugene L Griessel

A popular vote does not confer wisdom, intelligence or morality.

- I usually post only from Sci.Military.Naval -

_ wrote:
Most recent estimate is that the probability of impact of 2007 WD5 with
mars is about 4%.

If it does not hit, it might be really close; what are the chances that its
orbit would be greatly changed?

Depends on the distance b at closest approach. The planet-centered
bending angle is something like arctan (GM/bv^2), which for an incoming
velocity of 13.5 km/s yields an angle of at most 4 degrees. That's
equivalent to a delta V of around 0.93 km/s. This would indeed make a
significant change to the heliocentric orbit, about 1 part in 13, with
all the orbital elements changing. (The heliocentric distance at the
encounter longitude would be about the only thing not to change.)

Impact velocity is estimated to be (if occuring) 13.5 x10^3 m/s. Is it
possible that it could become a third martian moon(let)?

Not unless there's enough aerobraking to capture it into orbit, and the
chances of being that lucky are minuscule. Lithobraking is much more
likely. grin The object is coming in on a hyperbolic orbit, and if
there's no collision it will leave on a hyperbolic orbit. Or to put it
another way, in order for an incoming object to be captured, it must
shed a lot of energy somehow.

-- Bill Owen

On Sat, 29 Dec 2007 01:09:32 GMT, _
wrote:

Most recent estimate is that the probability of impact of 2007 WD5 with
mars is about 4%.

If it does not hit, it might be really close; what are the chances that its
orbit would be greatly changed?

Its orbit _will_ be affected, probably significantly. Nobody is
projecting what the orbit will look like after the encounter- with the
current uncertainty in position nobody knows.

Impact velocity is estimated to be (if occuring) 13.5 x10^3 m/s. Is it
possible that it could become a third martian moon(let)?

Almost impossible. Too much velocity would have to be lost. The only way
it could be captured would be through an extraordinarily unlikely
aerobraking passage.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

On Fri, 28 Dec 2007 17:28:49 -0800, Bill Owen wrote:

The object is coming in on a hyperbolic orbit, and if
there's no collision it will leave on a hyperbolic orbit.

The orbit is elliptical, with e=0.6. Nowhere near hyperbolic. Its
velocity is also far less than the solar escape velocity, so barring an
unlikely very close encounter, it's likely to leave with an elliptical
orbit as well, having either gained or shed a little velocity.

Even a slight change in its orbital elements may profoundly impact (no
pun intended) its chances of future collisions with either Earth or
Mars. This is an Apollo class asteroid with a period just under five
years.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote:
On Fri, 28 Dec 2007 17:28:49 -0800, Bill Owen wrote:

The object is coming in on a hyperbolic orbit, and if
there's no collision it will leave on a hyperbolic orbit.

The orbit is elliptical, with e=0.6. Nowhere near hyperbolic.

snip

When I read Bill's post I assumed he meant hyperbolic WRT Mars.
If I understand correctly, "hyperbolic orbit" is something of an oxymoron.


Shawn

On Fri, 28 Dec 2007 20:15:57 -0700, Shawn wrote:

When I read Bill's post I assumed he meant hyperbolic WRT Mars.
If I understand correctly, "hyperbolic orbit" is something of an oxymoron.

It might sort of give that appearance, but even with respect to Mars you
wouldn't call it hyperbolic. The asteroid isn't orbiting Mars, and is
likely to pass the planet again in the future.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote:
On Fri, 28 Dec 2007 20:15:57 -0700, Shawn wrote:

When I read Bill's post I assumed he meant hyperbolic WRT Mars.
If I understand correctly, "hyperbolic orbit" is something of an oxymoron.

It might sort of give that appearance, but even with respect to Mars you
wouldn't call it hyperbolic. The asteroid isn't orbiting Mars, and is
likely to pass the planet again in the future.

I don't see the point in your nitpick. Of course it can be looked at as
a hyperbolic trajectory with respect to Mars, at least during the
encounter. In considering a possible capture it's not an unreasonable
way to look at it.

As for capture, people often don't realize that for two bodies (as in
the case of a planet and a passing asteroid) gravity alone usually isn't
sufficient for the asteroid to be captured. As I understand it you
either need an interaction with a third body or some other affect, such
as the aerobraking already mentioned.

Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com

To reply take out your eye

On Fri, 28 Dec 2007 23:41:54 -0700, Greg Crinklaw
wrote:

I don't see the point in your nitpick. Of course it can be looked at as
a hyperbolic trajectory with respect to Mars, at least during the
encounter. In considering a possible capture it's not an unreasonable
way to look at it.

I don't think it's a nitpick. The exact meaning of the statement was
unclear. Certainly, the actual orbit is not hyperbolic, which is what
was stated and which could be confusing. Likewise, the asteroid is not
in any kind of orbit around Mars, hyperbolic or otherwise. And even with
respect to Mars, I don't believe the shape of the path could be
described as hyperbolic. I think it's more of a distorted ellipse.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote:
On Fri, 28 Dec 2007 23:41:54 -0700, Greg Crinklaw
wrote:

I don't see the point in your nitpick. Of course it can be looked at as
a hyperbolic trajectory with respect to Mars, at least during the
encounter. In considering a possible capture it's not an unreasonable
way to look at it.

I don't think it's a nitpick. The exact meaning of the statement was
unclear. Certainly, the actual orbit is not hyperbolic, which is what
was stated and which could be confusing. Likewise, the asteroid is not
in any kind of orbit around Mars, hyperbolic or otherwise. And even with
respect to Mars, I don't believe the shape of the path could be
described as hyperbolic. I think it's more of a distorted ellipse.

I think you just like to argue...

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing: http://www.skyhound.com/sh/skyhound.html
Comets: http://comets.skyhound.com

To reply take out your eye