21

I kept wondering where this 72 km/s maximum is coming from, and I figured it out! This is the calculation: Why? Firstly, it's obvious that the Earth is traveling at 30 km/s in its orbit. But what possible directions can the asteroid hit from? The most logical approach is to hit it moving the exactly opposite direction. That means we demand an asteroid ...


21

Finding macroscopic (i.e., big enough to actually use) pure-iron meteoroids appears to be extremely low-probability. Certainly the bulk composition of the metals in Earth (good references here, here, and here) and metallic meteorites is iron plus nickel, a siderophile, and a few also-rans, like sulfur and oxygen, and other siderophile metals like cobalt. ...


20

Yes, NASA definitely takes meteor showers seriously and has delayed one Space Shuttle mission due to colliding dates with predicted peaks of meteoritic activity, and was somewhat concerned about the future launch window for another mission, that later launched just a day shy of a peak of a meteor shower: In August 1993, the launch of Space Shuttle Discovery ...


16

I just want to add that a lot of work goes into predictions of abundance, for objects including those we have not detected so far. There is some similarity to exoplanets - where we know that a method has a detection bias. If you can quantify the detection bias perfectly, then you can get the total abundance for different sizes. One source gives a pretty ...


15

If it is more dangerous, how much more and in what ways? Proffesorfish and Eli Skolas have both given thoughtful answers comparing the hazards of I.S.S. vs Moonbase. If humans were preceded by robots to establish infra-structure, I believe a moonbase could be less hazardous. Radiation shielding from local resources could be added to Bigelow habs. At the ...


11

Sure it's possible. There is two ways for this to be achieved: For an earth satellite; cancel all forward velocity. The satellite will then start being attracted by earth gravity and fall straight down (minus moon's orbital perturbation, ...) For an object coming from outside the earth gravity well, to move faster or slower, in a similar axis as the ...


9

Asteroids, Meteorites, and Comets has this to say: Meteorites between the size of a grain of sand and about four inches (10 cm) in diameter create a bright light trail and usually burn up in the atmosphere. Meteorites between about four inches (10 cm) and 3 feet (1 m) may survive the burning of entry to land on the Earth's surface. Meteorites ...


8

Obligatory XKCD Forgive me for assuming this, but it seems like you don't quite understand what an orbit is. As XKCD Puts it "Space is not up, space is sideways very, very fast." To put it another way, if I hold a ball in my hand and drop it, it will go straight down. If I flick the ball a little bit, it'll follow a very steep arc - still mostly down. If ...


8

This answer and question on physics cover a similar topic, I will link to it here and block quote the most relevant parts. The most notable part of this answer is most likely going to be: Asteroids are not distributed uniformly in the asteroid belt, but could be approximated to be evenly spaced in a region from 2.2 AU (1 AU is 93 million miles, or the ...


7

The majority of the rocks from Mars appear to have come from a single impact on Mars, which formed Mojave Crater. I'm finding it difficult to get an exact power for that impact, but the crater is 58 km in diameter. It is a very large crater, one of the type that rarely impacts anywhere. Discovering a Veneran meteorite would be quite rate, as LocalFluff ...


7

Here's a rough estimate. From the curves at top left of the plot in figure 1 in this paper, we can expect on average, per year per million km2 of earth surface, 4.5 meteors, weighing 31 grams ("log m" -- base 10, not base e, which would mean 7 grams). Heavier ones are rarer. Your 500 m diameter balloon's projected area is about 0.2 km2. So the average ...


6

People did! Re-reading the linked article in ASU's Red Planet Report, I noticed at the end it links to an additional article; "More on Egg Rock here". That link says: Laser-zapping of a globular, golf-ball-size object on Mars by NASA’s Curiosity rover confirms that it is an iron-nickel meteorite fallen from the Red Planet’s sky. Iron-nickel ...


6

According to the American Meteor Society, meteorites usually hit the Earth's atmosphere going around 160,000 MPH. Meteors enter the atmosphere at speeds ranging from 11 km/sec (25,000 mph), to 72 km/sec (160,000 mph!)... The 70~ish top figure is also repeated in this answers.com answer. Why such a big range, between 25k and 160k MPH? The wide range ...


6

Between the orbit of Mars and Jupiter, you can find the Asteroid Belt. The total mass of all of the asteroids is about 4% that of the Moon. About 10% of the mass is thought to be M-type (metal-rich) asteroids. Some of the asteroids like 16 Psyche are made up of mostly metals like iron and nickel. NASA is planning a mission, Psyche to explore this minor ...


6

I'm highly skeptical that a 99.99% pure iron meteorite would be a fragment of a natural solar system object. It's more likely you have a shard, maybe part of a bolt or some such (hmm, I just thought, even a bolt would be steel, not pure iron—maybe a part of a magnetic device?), from some re-entering satellite. Natural metal meteorites are never pure iron, ...


5

To plug the numbers given into a simple calculation: The asteroid belt has a volume of 4,35E25 km^3. If we assume for a moment that the asteroids are evenly spaced, and there are 15 billion asteroids (estimate given above for sizes 0,1km+), we arrive at roughly 180km distance from asteroid to asteroid. 3 Orders of magnitude in the number of asteroids give us ...


5

ISS and a Moon base are equally safe. As long as they don't suddenly explode or otherwise become death traps because of some technical malfunction in the human artefacts themselves, regardless of the space environment. Among all the innovative suggestions about what could be dangerous, I want to remind of the fact that the only thing which has killed ...


5

There should be. It needs a huge impact on Earth to send material all the way to Mars but we get them occasionally. You need something of the order of the Chicxulub impact 66 million years ago. The debris would take about a hundred years, for the first material to get there and the material would continue to arrive on Mars for up to 20 million years from ...


4

As it turns out, perchlorate is actually rather unreactive under Martian surface conditions, and this actually explains the unusual abundance of perchlorate there: In any case, most of the chlorine has been oxidized as far as possible because the chlorine within perchlorate has a maximal +7 oxidation number. From a thermodynamic perspective, this makes ...


4

There is a network of satellites designed to detect ballistic missile launches. The key feature in each of these is very high temperatures moving at fast speeds. Thus, the easiest way to look for them is to look in the infrared for relatively high temperatures. It just so turns out that this is exactly the same kind of thing that an asteroid impact in the ...


3

One possibility is to launch straight up. Read about sounding rockets and Blue Origin New Sheppard vehicle. If you launch straight up and do not reach escape velocity, you will come almost straight down. Almost because the Earth rotates under you and when you leave the atmosphere you are no longer affected by that rotation. Then falling down you will reach ...


3

Space debris is tracked via radar. Asteroids are usually tracked via optical telescopes set up for that purpose. If they get really close to Earth, they may be tracked via the space debris systems too. In some cases, extra observations are arranged for asteroids that look like they may get close to Earth. Meteoroids are too small to be tracked at long ...


3

- Is there a probability of discovering a Venerean meteorite here on Earth? Possible but unlikely. No (known) venerean meteorite has been found on Earth. Several factors make it much more unlikely than a meteorite from Mars (I should write "much less common", certainly some are around, but so few that we might never find them). Venus' deeper gravity well ...


3

Apart from the points were an actual asteroid is, the density is very low. "Contrary to popular imagery, the asteroid belt is mostly empty. The asteroids are spread over such a large volume that it would be improbable to reach an asteroid without aiming carefully." (source) Furthermore the distribution of the asteroids is not uniform, thus the mean density ...


3

I have very good information for you! I confirm that there is pure iron in space because I have a 99% iron meteorite. This samples weight 42,38g, and the fusion crust is no longer visible because I have several acid tests, before knowing that it should be kept. This is the certificate of analysis. Translation: Mr Siliman showed me four meteorite samples....


3

In the NPR News item and podcast Former Astronaut On Watching For Life-Destroying Objects From Space Reporter Lulu Garcia-Navarro interviews physicist and former NASA astronaut Ed Lu, currently the executive director of the B612 Foundation: GARCIA-NAVARRO: So we only just learned of this meteor because NASA only just now put up the information on its ...


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