https://www.space.com/mars-fresh-crater-nasa-mro-photo-2019.html

Images from the Mars Reconnaissance Orbiter show a fresh impact crater, some 15 metres across, that appeared some time between September 2016 and February 2019.

The colour images show the exposed basalt substrate, and a debris field some 2 km wide. The impactor is estimated to have been about 5 metres wide. Although it is not uncommon for the MRO to detect fresh craters, this is one of the largest it has found.

dv said:

https://www.space.com/mars-fresh-crater-nasa-mro-photo-2019.html

Images from the Mars Reconnaissance Orbiter show a fresh impact crater, some 15 metres across, that appeared some time between September 2016 and February 2019.

The colour images show the exposed basalt substrate, and a debris field some 2 km wide. The impactor is estimated to have been about 5 metres wide. Although it is not uncommon for the MRO to detect fresh craters, this is one of the largest it has found.

How do they know its not mallee fowl.

Imagine if they could use modern technology to find MH370,

dv said:

https://www.space.com/mars-fresh-crater-nasa-mro-photo-2019.html

Images from the Mars Reconnaissance Orbiter show a fresh impact crater, some 15 metres across, that appeared some time between September 2016 and February 2019.

The colour images show the exposed basalt substrate, and a debris field some 2 km wide. The impactor is estimated to have been about 5 metres wide. Although it is not uncommon for the MRO to detect fresh craters, this is one of the largest it has found.

Smashing!

^heh

Terrific. Thanks dv.

:)

Interesting that the crater is only three times the estimated size of the impactor.

How wide a crater would a 5 metre object make on Earth, at usual impact speeds?

Bubblecar said:

Interesting that the crater is only three times the estimated size of the impactor.

How wide a crater would a 5 metre object make on Earth, at usual impact speeds?

True story: a 5 metre meteoroid will not reach the Earth’s surface intact. There will be an airburst and small pieces will fall over a wide area. Even the Chelyabinsk object, some 20 m across, got shredded in the atmosphere.

For an impactor to reach the ground at high speed you’d need it to be at least 75 or so metres across: a rare event. The craters formed by Earth impactors are typically around 10 to 15 times the diameter of the objects that create them.

As to why this Martian one is only 3 times, I can think of 3 possible reasons. A) Even in the thin Martian atmosphere a small object such as this would be significantly slowed. B) This appears to have landed on a place with a shallow and hard bedrock (ancient basalt). C) Mars’s“gravity well” is shallower than Earth’s due to its lower mass (about 1/10 Earth’s) so, like for like, I’d expect the incoming speed of the object to be 3000 to 5000 metres per second slower than a similar object intercepted by the Earth.

Bubblecar said:

Interesting that the crater is only three times the estimated size of the impactor.

How wide a crater would a 5 metre object make on Earth, at usual impact speeds?

That’s a very good question, and there are two parts to it.

• Would a 5 metre object burn up in the atmosphere?
• If the part that made it through the atmosphere was 5 metres across, how big would the crater be in rock / in sand?

dv said:

Bubblecar said:

Interesting that the crater is only three times the estimated size of the impactor.

How wide a crater would a 5 metre object make on Earth, at usual impact speeds?

True story: a 5 metre meteoroid will not reach the Earth’s surface intact. There will be an airburst and small pieces will fall over a wide area. Even the Chelyabinsk object, some 20 m across, got shredded in the atmosphere.

For an impactor to reach the ground at high speed you’d need it to be at least 75 or so metres across: a rare event. The craters formed by Earth impactors are typically around 10 to 15 times the diameter of the objects that create them.

As to why this Martian one is only 3 times, I can think of 3 possible reasons. A) Even in the thin Martian atmosphere a small object such as this would be significantly slowed. B) This appears to have landed on a place with a shallow and hard bedrock (ancient basalt). C) Mars’s“gravity well” is shallower than Earth’s due to its lower mass (about 1/10 Earth’s) so, like for like, I’d expect the incoming speed of the object to be 3000 to 5000 metres per second slower than a similar object intercepted by the Earth.

OK ta.

Bubblecar said:

dv said:

Bubblecar said:

Interesting that the crater is only three times the estimated size of the impactor.

How wide a crater would a 5 metre object make on Earth, at usual impact speeds?

True story: a 5 metre meteoroid will not reach the Earth’s surface intact. There will be an airburst and small pieces will fall over a wide area. Even the Chelyabinsk object, some 20 m across, got shredded in the atmosphere.

For an impactor to reach the ground at high speed you’d need it to be at least 75 or so metres across: a rare event. The craters formed by Earth impactors are typically around 10 to 15 times the diameter of the objects that create them.

As to why this Martian one is only 3 times, I can think of 3 possible reasons. A) Even in the thin Martian atmosphere a small object such as this would be significantly slowed. B) This appears to have landed on a place with a shallow and hard bedrock (ancient basalt). C) Mars’s“gravity well” is shallower than Earth’s due to its lower mass (about 1/10 Earth’s) so, like for like, I’d expect the incoming speed of the object to be 3000 to 5000 metres per second slower than a similar object intercepted by the Earth.

OK ta.

Not quite OK. For Earth.

A comet or rubble pile asteroid 5 metres across would not reach the ground.
An ordinary chondrite or carbonaceous chondrite would shatter in the atmosphere, but shards of it would reach the ground.
A lump of pure iron-nickel on the other hand, I’d have to look that up to find out if it would reach the ground. I’m pretty sure it would hit in one piece.

There’s also the issue of orbit. A comet would hit at about 30 km/s. An asteroid would hit at about half that, 15 km/s. A near-earth asteroid would hit at more like 6 km/s. Given that energy is proportional to the square of the velocity, that difference in speed makes a difference.

A comet would hit Mars at about 24 km/s, and an asteroid at about 5 km/s.

Calculate the relationship between impactor size and crater size using the calculator on http://simulator.down2earth.eu/planet.html?lang=en-GB

You can do it for Mars, Earth and Moon. Give it a try.

Unfortunately, that doesn’t allow me to set a projectile diameter smaller than 100 metres.

For Earth, this is better.
https://www.purdue.edu/impactearth/

A 5 m diameter iron asteroid hitting Earth at 15 km/s would break up in the Earth’s atmosphere, but the fragments would hit the ground at 6 km/s creating a crater field.