Starship Asterisk*

JohnD wrote:

Chris Peterson wrote:

JohnD wrote:Meteoric iron would be nice. But landing at the usual speed for a meteor, with almost no atmosphere to slow it down would crater the bedrock and spread the meteor across the Marscape as vapour, condensing to dust. Is there a mechanism for a slow speed landing?

Yeah. The atmosphere. The rovers have found many meteorites sitting on the surface. On Mars, meteoroids which survive burning up in the upper atmosphere fall with a terminal velocity on the order of five to ten times that on Earth, still below the speed of sound and too slow to cause cratering. (Recall that Martian landers typically use parachutes for part of their landing sequence.)

Chris,
But something the size of Ireson Hill?

JohnD wrote:
But Ireson Hill is intact and there is no crater.
Therefore Ireson is not a meteorite.

Chris Peterson wrote:

JohnD wrote:Meteoric iron would be nice. But landing at the usual speed for a meteor, with almost no atmosphere to slow it down would crater the bedrock and spread the meteor across the Marscape as vapour, condensing to dust. Is there a mechanism for a slow speed landing?

Yeah. The atmosphere. The rovers have found many meteorites sitting on the surface. On Mars, meteoroids which survive burning up in the upper atmosphere fall with a terminal velocity on the order of five to ten times that on Earth, still below the speed of sound and too slow to cause cratering. (Recall that Martian landers typically use parachutes for part of their landing sequence.)

neufer wrote:

Chris Peterson wrote: (BTW, the correct term for material which survives ablation and is in the process of cold fall is "meteorite". Even before it hits the ground.)

• Meteoroid => Meteor => Meteorite

bystander wrote:It's not vertically stretched, it's horizontally compressed.

Chris Peterson wrote:
(BTW, the correct term for material which survives ablation and is in the process of cold fall is "meteorite". Even before it hits the ground.)

• Meteoroid => Meteor => Meteorite

https://en.wikipedia.org/wiki/Meteorite wrote:
<<A meteorite is a solid piece of debris from an object, such as a comet, asteroid, or meteoroid, that originates in outer space and survives its passage through the Earth's atmosphere and impact with the Earth's surface or that of another planet. When the object enters the atmosphere, various factors like friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate that energy. It then becomes a meteor and forms a fireball, also known as a shooting star or falling star; astronomers call the brightest examples "bolides." Meteorites that survive atmospheric entry and impact vary greatly in size. For geologists, a bolide is a meteorite large enough to create a crater.>>

https://en.wikipedia.org/wiki/Meteoroid wrote:
<<A meteoroid is a small rocky or metallic body in outer space. Meteoroids are significantly smaller than asteroids, and range in size from small grains to 1 meter-wide objects. Objects smaller than this are classified as micrometeoroids or space dust. Most are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars.>>

https://en.wikipedia.org/wiki/Asteroid#Terminology wrote:
<<Traditionally, small bodies orbiting the Sun were classified as comets, asteroids, or meteoroids, with anything smaller than 10 meters across being called a meteoroid (such as in Beech and Steel's 1995 paper). The term "asteroid", from the Greek word for "star-like", never had a formal definition, with the broader term minor planet being preferred by the International Astronomical Union. However, following the discovery of asteroids below 10 meters in size, Rubin and Grossman in a 2010 paper revised the previous definition of meteoroid to objects between 10 µm and 1 meter in size in order to maintain the distinction between asteroids and meteoroids.>>

neufer wrote:

Chris Peterson wrote:Sure. But even under current conditions, the atmospheric density in Earth's atmosphere at the point where meteorites [sic] are typically in free fall (they have lost their initial velocity) corresponds to a height in the Martian atmosphere of about 10 km.

That sort of depends on the size of the meteor [sic].

Chris Peterson wrote:

neufer wrote:

Chris Peterson wrote:
Yeah. The atmosphere. The rovers have found many meteorites sitting on the surface. On Mars, meteoroids which survive burning up in the upper atmosphere fall with a terminal velocity on the order of five to ten times that on Earth, still below the speed of sound and too slow to cause cratering. (Recall that Martian landers typically use parachutes for part of their landing sequence.)

Meteoric iron in the past could also have been slowed by:

• 1) a thicker atmosphere
  2) a crater lake and/or
  3) the sediment left by that lake.

Sure. But even under current conditions, the atmospheric density in Earth's atmosphere at the point where meteorites [sic] are typically in free fall (they have lost their initial velocity) corresponds to a height in the Martian atmosphere of about 10 km.

geoffrey.landis wrote:Really. This is not a feature on Mars.

neufer wrote:

Chris Peterson wrote:

JohnD wrote:
Meteoric iron would be nice. But landing at the usual speed for a meteor, with almost no atmosphere to slow it down would crater the bedrock and spread the meteor across the Marscape as vapour, condensing to dust. Is there a mechanism for a slow speed landing?

Yeah. The atmosphere. The rovers have found many meteorites sitting on the surface. On Mars, meteoroids which survive burning up in the upper atmosphere fall with a terminal velocity on the order of five to ten times that on Earth, still below the speed of sound and too slow to cause cratering. (Recall that Martian landers typically use parachutes for part of their landing sequence.)

Meteoric iron in the past could also have been slowed by:

• 1) a thicker atmosphere
  2) a crater lake and/or
  3) the sediment left by that lake.

Chris Peterson wrote:

JohnD wrote:
Meteoric iron would be nice. But landing at the usual speed for a meteor, with almost no atmosphere to slow it down would crater the bedrock and spread the meteor across the Marscape as vapour, condensing to dust. Is there a mechanism for a slow speed landing?

Yeah. The atmosphere. The rovers have found many meteorites sitting on the surface. On Mars, meteoroids which survive burning up in the upper atmosphere fall with a terminal velocity on the order of five to ten times that on Earth, still below the speed of sound and too slow to cause cratering. (Recall that Martian landers typically use parachutes for part of their landing sequence.)

• 1) a thicker atmosphere
  2) a crater lake and/or
  3) the sediment left by that lake.

JohnD wrote:Meteoric iron would be nice. But landing at the usual speed for a meteor, with almost no atmosphere to slow it down would crater the bedrock and spread the meteor across the Marscape as vapour, condensing to dust. Is there a mechanism for a slow speed landing?

geoffrey.landis wrote:
Really. This is not a feature on Mars.

• Cross over Bar Harbor & follow the blueberries:

http://sheltontrails.blogspot.com/2014/08/bar-harbor-blueberry-barrens.html wrote:
<<One of our fondest memories of Bar Harbor Campground is the hillside covered in blueberries overlooking Frenchman's Bay to the north. "Blueberry Barrens" are described by the State of Maine on their website, and I think this hillside fits that description.

May I digress about the rock? It's always there, just under foot, and it clearly plays a major part in how things grow here. I've never known quite what it was, but it's very different from the rest of the island, nothing like the famous pink granite of Cadillac Mountain. The geology map says it's the Bar Harbor Formation, which is composed of sandstones and siltstones that often show obvious bedding layers. I now see the bedrock maps says this is "Ireson Hill": "The rocks found along the shore at The Ovens and in the road-cuts along Route 3 at Ireson Hill on the northern side of the island also belong to the Bar Harbor Formation, but here the rock is flint-like and bedding is difficult or impossible to see. Some of these rocks are believed to be accumulations of ash that settled out of the atmosphere after a volcanic eruption." >>

http://tolkiengateway.net/wiki/Smials wrote:
Smials were the hobbit-holes tunelled into earth mounds and hills.

• "Smials. A word peculiar to hobbits (not Common Speech), meaning 'burrow'; leave unchanged. It is a form that the Old English word smygel 'burrow' might have had, if it had survived. The same element appears in Gollum's real name, Sméagol."
  ― Tolkien
  
  "In a hole in the ground there lived a Hobbit. Not a nasty, dirty, wet hole, filled with the ends of worms and oozy smell, nor yet a dry, bare, sandy hole with nothing in it to sit down on or to eat: it was a hobbit-hole and that means comfort."
  ― The Hobbit, "An Unexpected Party"

For generations the Hobbits, made diggings in the earth to live. By the later Third Age the poorest Hobbits still went on living in burrows of the most primitive kind with only one window or none. For the most well-to-do hobbits, smials were luxurious versions of those primitive diggings of old. Their tunnels had rounded walls and branched to other rooms. Smials included Bag End and the smials along Bagshot Row of Hobbiton, the Great Smials of Tuckborough and Brandy Hall. The latter two were large enough to have ample room for a hundred Hobbits.>>

bls0326 wrote:I like the "uncompressed" version of the today's picture better.