Comet observation from Mars, comets close encounters to Mars in 2013 and 2014 |
Comet observation from Mars, comets close encounters to Mars in 2013 and 2014 |
Feb 25 2013, 10:07 PM
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#1
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Newbie Group: Members Posts: 18 Joined: 20-April 05 From: Czech Republic Member No.: 300 |
Is there is any possibility to observe comets in near future from surface of Mars and/or from Mars orbiters. Which types of instruments are possible to use?
For example (http://ssd.jpl.nasa.gov/horizons.cgi - position Mars 0deg Longitude, 5deg south Latitude, time UTC): 1) Comet C/2012 S1 (ISON) 2013-Oct-01 17:19UTC RA 23 07 44.73 DE +69 27 46.0 MAG 2.93 r 1.637007919902 delta 0.07246306543080 So there is relativly very close encounter in October 2013, about 11 million km from Mars.. 2) Comet C/2013 A1 (Sidding Spring) 2014-Oct-19 20:59UTC RA 10 49 50.64 DE -60 38 09.5 MAG -8.29 r 1.401218071277 delta 0.00070643344409 There is still maybe not so precise orbit BUT, there is ONLY about 105 000 km (65 000 miles) encounter from Mars. Especially the second comet, if this orbit will be OK, is very interesting target to observe. -------------------- |
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Feb 28 2013, 04:31 PM
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#2
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Senior Member Group: Members Posts: 4256 Joined: 17-January 05 Member No.: 152 |
We've made (and survived) many comet encounters with several spacecraft, at distances of several hundred km down to a couple hundred km (Deep Impact, Stardust, etc). Those were smaller comets, but Giotto survived the Halley encounter at about 600 km. Of course those missions were designed for comet encounters, not for Mars orbit.
My guess, based on flux conservation, is that the density of particles in the coma drops like roughly the inverse square of the distance from the Of course this is still early days, and brightness estimates will be improved. Most crucially, as mcaplinger said, orbital elements will be improved. The big question now is what is the uncertainty in the close-approach Mars distance? The blog quoted above stated that the comet "might pass just 41,000 km... from the planet’s centre". Is that a lower limit? What's the upper limit? That would give us a better sense of what the Mars close-approach distance will be. Anyway, based on these numbers, I'd expect no real concern for the orbiters, and even less for the rovers. And I too can't wait for this encounter! |
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Mar 1 2013, 12:38 AM
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#3
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Senior Member Group: Members Posts: 1591 Joined: 14-October 05 From: Vermont Member No.: 530 |
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Mar 4 2013, 06:11 AM
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#4
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Member Group: Members Posts: 613 Joined: 23-February 07 From: Occasionally in Columbia, MD Member No.: 1764 |
Mostly. With a Whipple shield. The VEGAs actually fared less well in some respects, even though they were 10 times further out than Giotto (maybe encountered a jet?) http://www.lpl.arizona.edu/~rlorenz/solararraydamage.pdf |
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Mar 4 2013, 06:24 AM
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#5
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Member Group: Members Posts: 813 Joined: 8-February 04 From: Arabia Terra Member No.: 12 |
Belatedly realised that what I said above was pretty silly. Was trying to think of young (<100Ma) craters in the inner solar system that are around 200km in diameter or greater, and for some reason the word 'Chicxulub' never occurred to me...
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Mar 5 2013, 09:45 PM
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#6
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Senior Member Group: Members Posts: 2530 Joined: 20-April 05 Member No.: 321 |
To SFJCody's interesting thoughts about the unlikelihood of seeing a very large impact in our lifetime, I think the key points are:
1) Near misses, if you define them as having about 250x the cross section of the planet, will happen almost 250x more often than actual events. If Chicxulub events occur every 50 million years at Earth, there will a Chicxulub-sized near miss every 200K years. 2) If you count four bodies (Venus, Earth, the Moon, and Mars) as targets of interest, you divide that roughly by four, so every 50K years. 3) The martian cratering rate, per unit surface area, is about 2x the Moon's. But for near misses of a given distance, surface area is irrelevant, and we get a martian rate of about 8x the Moon's. So for Mars alone, we expect one such event every 25K years. 4) The pass is not known to be this close and we'd have to integrate over the possible trajectories to rate it fairly, but this may be considerably further, and so we get further reduction. 5) A generalization/extension of (3): There's a logical fallacy of taking the most unlikely thing that you observe/forecast and noting how weird it is that it happen. What was the probability that you would receive the phone number you were assigned at random? Near zero for that precise number, but the probability that you would get A number about which you could make that comment is near unity. The solar system allows for many weird catastrophic events that could happen, and cumulatively the probability of one of them happening is much higher than the probability of any one of them. We could have seen a collision form Saturn's rings, but we didn't. We could have seen volcanic activity repave Venus's whole surface during our lifetimes but we didn't. We could be seeing a nearby red giant go supernova but we're not. Given that the Mars event is looking like a once-every-few-thousand-years event and there are innumerable comparably striking (no pun intended) events we could make the same comment about, it doesn't seem so strange that we're seeing one of them. |
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