by neufer » Wed Apr 04, 2018 4:27 pm
Chris Peterson wrote: ↑Wed Apr 04, 2018 3:38 pm
RocketRon wrote: ↑Wed Apr 04, 2018 5:22 am
How much harder do meteorites strike the surface of Mars because of its thin atmosphere,
compared to say on Earth. Anyone done the calcs, size for size ?
Ordinary meteorites (that is, rocks the size of gravel to boulders) fall somewhat faster than they do on Earth because Mars's thin atmosphere results in a higher terminal velocity. But these are still subsonic, non-crater forming impacts. The survival rate may be somewhat higher on Mars because of the thinner atmosphere, but probably not by much. Most bodies still burn up in the atmosphere, just like here on Earth.
Not quite sure what you mean by "
boulders."
The well documented 4-meter 2008 TC3 stony meteor exploded at an estimated altitude of 37 kilometers where the pressure is ~4.2 mb.
A smaller (2-meter diameter) slower iron meteor would surely make it all the way to the ~6 mb Martian surface to create a ~20 meter crater.
https://en.wikipedia.org/wiki/2008_TC3 wrote:
<<2008 TC3 was an 80-metric-ton, 4.1-meter diameter asteroid that entered Earth's atmosphere on October 7, 2008. It exploded at an estimated 37 kilometers above the Nubian Desert in Sudan. Some 600 meteorites, weighing a total of 10.5 kilograms, were recovered; many of these belonged to a rare type known as ureilites, which contain, among other minerals, nanodiamonds. It was the first time that an asteroid impact had been predicted prior to its entry into the atmosphere as a meteor.
The meteor entered Earth's atmosphere above northern Sudan at 02:46 UTC (05:46 local time) on October 7, 2008 with a velocity of 12.8 km/s at an azimuth of 281 degrees and an altitude angle of 19 degrees to the local horizon. It exploded tens of kilometers above the ground with the energy of 0.9 to 2.1 kilotons of TNT over a remote area of the Nubian Desert, causing a large fireball or bolide.
The Times reported that the meteor's "light was so intense that it lit up the sky like a full moon and an airliner 1,400 km away reported seeing the bright flash." A low-resolution image of the explosion was captured by the weather satellite Meteosat 8. The Meteosat images place the fireball at 21.00°N 32.15°E. Infrasound detector arrays in Kenya also detected a sound wave from the direction of the expected impact corresponding to energy of 1.1 to 2.1 kilotons of TNT. Asteroids of this size hit Earth about two or three times a year.>>
[quote="Chris Peterson" post_id=281235 time=1522856330 user_id=117706]
[quote=RocketRon post_id=281222 time=1522819342]
How much harder do meteorites strike the surface of Mars because of its thin atmosphere,
compared to say on Earth. Anyone done the calcs, size for size ?
[/quote]
Ordinary meteorites (that is, rocks the size of gravel to boulders) fall somewhat faster than they do on Earth because Mars's thin atmosphere results in a higher terminal velocity. But these are still subsonic, non-crater forming impacts. The survival rate may be somewhat higher on Mars because of the thinner atmosphere, but probably not by much. Most bodies still burn up in the atmosphere, just like here on Earth.[/quote]
Not quite sure what you mean by "[b][i]boulders[/i][/b]."
The well documented 4-meter 2008 TC3 stony meteor exploded at an estimated altitude of 37 kilometers where the pressure is ~4.2 mb.
A smaller (2-meter diameter) slower iron meteor would surely make it all the way to the ~6 mb Martian surface to create a ~20 meter crater.
[quote=" https://en.wikipedia.org/wiki/2008_TC3"]
[float=left][img3="Animation of 2008 TC3's excited rotation prior to entering Earth's atmosphere."]https://upload.wikimedia.org/wikipedia/commons/8/8c/2008_TC3_Tumbling_%28reduced%29.gif[/img3][/float]<<2008 TC3 was an 80-metric-ton, 4.1-meter diameter asteroid that entered Earth's atmosphere on October 7, 2008. It exploded at an estimated 37 kilometers above the Nubian Desert in Sudan. Some 600 meteorites, weighing a total of 10.5 kilograms, were recovered; many of these belonged to a rare type known as ureilites, which contain, among other minerals, nanodiamonds. It was the first time that an asteroid impact had been predicted prior to its entry into the atmosphere as a meteor.
The meteor entered Earth's atmosphere above northern Sudan at 02:46 UTC (05:46 local time) on October 7, 2008 with a velocity of 12.8 km/s at an azimuth of 281 degrees and an altitude angle of 19 degrees to the local horizon. It exploded tens of kilometers above the ground with the energy of 0.9 to 2.1 kilotons of TNT over a remote area of the Nubian Desert, causing a large fireball or bolide.
The Times reported that the meteor's "light was so intense that it lit up the sky like a full moon and an airliner 1,400 km away reported seeing the bright flash." A low-resolution image of the explosion was captured by the weather satellite Meteosat 8. The Meteosat images place the fireball at 21.00°N 32.15°E. Infrasound detector arrays in Kenya also detected a sound wave from the direction of the expected impact corresponding to energy of 1.1 to 2.1 kilotons of TNT. Asteroids of this size hit Earth about two or three times a year.>>[/quote]