(meteorobs) Re: Meteor picture from Mars?

[Pavol Habuda]

1. Entry velocities on Mars are in range from 5 up to 55 km/s.
Lower end is caused escape velocity from planet, upper velocity
of body on parabolic orbit strikes Mars directly head on 
(body is coming from apex).

2. Surface pressure on Mars is 1kPa. Comparing to Earth`s atmosphere,
pressure in 80 km on Earth is equal pressure in 50 km on Mars.
If we account lower temperatures on Mars, meteors glow in heights
between 40 and 60 km. That is my rough estimate.

3. Magnitude of meteor depends on his velocity. Meteor 0 mag at
velocity 70 km/s is about 6 mag bright at entry velocity 10 km/s.
I used simplified model with dependence m \propto -2.5 log(v).
   So, if Leonids would have entry velocities 10 km/s, then 
we never see meteor storm but only a few meteors per hour.
If average velocity decrease from 60 to 45 km/s, average magnitude
decrease of 1 mag. If average population index is 2.5, ZHR
then decrease about 3.3-times (2.5*(60/45)). 

Pavol Habuda

--- Ed Majden <epmajden at shaw.ca> wrote:

> on 6/11/05 1:22, Pavol Habuda at bzucino at yahoo.com wrote:
> 
> > Mars` atmosphere has less pressure than Earth`s. It means meteors glow
> > in lower heights than on Earth. I don`t see no other difference , except
> > lower entry velocities of meteoroids.
> > Lower velocities, as we know, result in much lower ZHR. So, we
> > would see less meteors on Mars than on Earth.
> > 
> > Physics must be the same, it means meteors look the same as on our planet.
> > 
> > Pavol Habuda
> > 
> 
> Paval:
> 
>     Why do you say meteoroids entering the atmosphere of Mars have lower
> entry velocity?  The velocity of a meteoroid is dependant on its orbit.  The
> more distant, the higher the velocity as in the case of shower meteoroids
> associated with comets than the ones associated with asteroids.  Yes, escape
> velocity is lower on Mars so entry velocity can be lower in some cases.  On
> Earth, entry velocity for meteoroids ranges from 72 km/sec down to 11.2
> km/sec which is the escape velocity of the Earth.  Mar's escape velocity is
> 5.0 km/sec so a meteoroid could be as slow as this on entry. If the
> meteoroid is in the same orbit, entry velocity on Mars would be a bit lower
> for the same meteoroid entering the Earth's atmosphere as Mars is further
> from the Sun than the Earth.  Perhaps this is what you were trying to point
> out.  It is true that meteoroids will become visible at a lower altitude on
> Mars because of the less dense atmosphere on this planet.  Can you explain
> why ZHR are lower with lower entry velocities?
> 
> Ed Majden
> 
> ---
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> meteorobs at meteorobs.org
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> 



		
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