Full Version: Asteroid on track for possible Mars hit
No way! That's nuts.
Oh, boy!!! 
If it hits, I wonder where...can't decide if one of the polar areas or one of ME's putative glacial areas would be more interesting... 
If it hits, I wonder where...can't decide if one of the polar areas or one of ME's putative glacial areas would be more interesting...
The story has been updated with the correct date for the potential encounter, Jan 30th.
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2007+WD5&orb=1 , set to Jan 30th, centered on Mars and zoomed in looks pretty exciting.
edit: The JPL Horizons system puts closest approach at 2008-Jan-30 09:10 at a distance of 51,722 km from the center of Mars (which is obviously too accurate considering the +/- in the asteroid's ephemeris)
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=2007+WD5&orb=1 , set to Jan 30th, centered on Mars and zoomed in looks pretty exciting.
edit: The JPL Horizons system puts closest approach at 2008-Jan-30 09:10 at a distance of 51,722 km from the center of Mars (which is obviously too accurate considering the +/- in the asteroid's ephemeris)
In the "funny coincidence" department, the Q&A section of the November/December issue of The Planetary Report contains a question on this very issue, namely the chances of a large object colliding with Mars in the near future. The interesting response is by Steve Chesley of JPL, who discussed the difficulties involved in tracking what he called "Mars Hazardous Asteroids" with the equipment currently available.
TTT
TTT
I think we need to generously apportion accolades to any active Mars mission team that manages to scan, image, probe, detect, sense or delve this rock with their spacecraft.
Checks on the current values in the JPL Horizon ephemeris at the Spirit and Opportunity sites indicate that it will be daytime at the Opportunity site at the time of closest approach of 2007 WD5, while it will be night at Spirit. At both sites the asteroid will be below the horizon at closest approach, but it will be above the horizon shortly thereafter at Spirit's site. Here are the Spirit results:
Date__(UT)__HR:MN R.A._(ICRF/J2000.0)_DEC Azi_(a-appr)_Elev APmag delta deldot
2008-Jan-30 09:11 01 15 23.28 +09 29 53.5 293.7580 -7.2526 11.16 .000347890218913 -0.4028331
2008-Jan-30 09:12 01 18 27.24 +09 50 57.9 293.7388 -6.6357 11.12 .000347765220082 -0.2203989
2008-Jan-30 09:13 01 21 31.69 +10 11 56.9 293.7171 -6.0183 11.09 .000347713435926 -0.0377873
2008-Jan-30 09:14 01 24 36.58 +10 32 49.7 293.6929 -5.4008 11.06 .000347734914938 0.1448863
2008-Jan-30 09:15 01 27 41.83 +10 53 35.4 293.6662 -4.7835 11.03 .000347829658025 0.3275060
2008-Jan-30 09:16 01 30 47.39 +11 14 13.4 293.6371 -4.1668 11.00 .000347997620976 0.5099566
2008-Jan-30 09:17 01 33 53.18 +11 34 42.8 293.6054 -3.5510 10.97 .000348238712257 0.6921231
2008-Jan-30 09:18 01 36 59.14 +11 55 03.0 293.5713 -2.9365 10.94 .000348552794951 0.8738916
2008-Jan-30 09:19 01 40 05.19 +12 15 13.3 293.5348 -2.3236 10.91 .000348939686995 1.0551493
2008-Jan-30 09:20 01 43 11.29 +12 35 13.0 293.4959 -1.7127 10.88 .000349399160625 1.2357853
2008-Jan-30 09:21 01 46 17.34 +12 55 01.4 293.4545 -1.1041 10.85 .000349930944870 1.4156906
2008-Jan-30 09:22 01 49 23.30 +13 14 37.8 293.4107 -0.4982 10.83 .000350534724486 1.5947582
2008-Jan-30 09:23 r 01 52 29.08 +13 34 01.7 293.3646 0.1048 10.80 .000351210142900 1.7728841
2008-Jan-30 09:24 01 55 34.63 +13 53 12.5 293.3161 0.7044 10.78 .000351956801419 1.9499668
2008-Jan-30 09:25 01 58 39.87 +14 12 09.5 293.2652 1.3004 10.76 .000352774261731 2.1259081
2008-Jan-30 09:26 02 01 44.74 +14 30 52.4 293.2121 1.8925 10.73 .000353662047016 2.3006133
2008-Jan-30 09:27 02 04 49.18 +14 49 20.5 293.1566 2.4804 10.71 .000354619642510 2.4739909
2008-Jan-30 09:28 02 07 53.12 +15 07 33.5 293.0989 3.0637 10.69 .000355646498321 2.6459536
2008-Jan-30 09:29 02 10 56.50 +15 25 30.8 293.0389 3.6423 10.67 .000356742029509 2.8164178
2008-Jan-30 09:30 02 13 59.26 +15 43 12.2 292.9768 4.2158 10.65 .000357905619227 2.9853041
Note that the asteroid will be rising in the West at about 293°. Of course, the details will change as the ephemeris is updated.
Steve M
CODE
Date__(UT)__HR:MN R.A._(ICRF/J2000.0)_DEC Azi_(a-appr)_Elev APmag delta deldot
2008-Jan-30 09:11 01 15 23.28 +09 29 53.5 293.7580 -7.2526 11.16 .000347890218913 -0.4028331
2008-Jan-30 09:12 01 18 27.24 +09 50 57.9 293.7388 -6.6357 11.12 .000347765220082 -0.2203989
2008-Jan-30 09:13 01 21 31.69 +10 11 56.9 293.7171 -6.0183 11.09 .000347713435926 -0.0377873
2008-Jan-30 09:14 01 24 36.58 +10 32 49.7 293.6929 -5.4008 11.06 .000347734914938 0.1448863
2008-Jan-30 09:15 01 27 41.83 +10 53 35.4 293.6662 -4.7835 11.03 .000347829658025 0.3275060
2008-Jan-30 09:16 01 30 47.39 +11 14 13.4 293.6371 -4.1668 11.00 .000347997620976 0.5099566
2008-Jan-30 09:17 01 33 53.18 +11 34 42.8 293.6054 -3.5510 10.97 .000348238712257 0.6921231
2008-Jan-30 09:18 01 36 59.14 +11 55 03.0 293.5713 -2.9365 10.94 .000348552794951 0.8738916
2008-Jan-30 09:19 01 40 05.19 +12 15 13.3 293.5348 -2.3236 10.91 .000348939686995 1.0551493
2008-Jan-30 09:20 01 43 11.29 +12 35 13.0 293.4959 -1.7127 10.88 .000349399160625 1.2357853
2008-Jan-30 09:21 01 46 17.34 +12 55 01.4 293.4545 -1.1041 10.85 .000349930944870 1.4156906
2008-Jan-30 09:22 01 49 23.30 +13 14 37.8 293.4107 -0.4982 10.83 .000350534724486 1.5947582
2008-Jan-30 09:23 r 01 52 29.08 +13 34 01.7 293.3646 0.1048 10.80 .000351210142900 1.7728841
2008-Jan-30 09:24 01 55 34.63 +13 53 12.5 293.3161 0.7044 10.78 .000351956801419 1.9499668
2008-Jan-30 09:25 01 58 39.87 +14 12 09.5 293.2652 1.3004 10.76 .000352774261731 2.1259081
2008-Jan-30 09:26 02 01 44.74 +14 30 52.4 293.2121 1.8925 10.73 .000353662047016 2.3006133
2008-Jan-30 09:27 02 04 49.18 +14 49 20.5 293.1566 2.4804 10.71 .000354619642510 2.4739909
2008-Jan-30 09:28 02 07 53.12 +15 07 33.5 293.0989 3.0637 10.69 .000355646498321 2.6459536
2008-Jan-30 09:29 02 10 56.50 +15 25 30.8 293.0389 3.6423 10.67 .000356742029509 2.8164178
2008-Jan-30 09:30 02 13 59.26 +15 43 12.2 292.9768 4.2158 10.65 .000357905619227 2.9853041
Note that the asteroid will be rising in the West at about 293°. Of course, the details will change as the ephemeris is updated.
Steve M
Here's the observational ephemeris from the Opportunity site. Note the asterisk indicating the Sun is above the horizon, and the x indicating the brightest interfering body (Phobos) is above the horizon.
Asteroid 2007 WD5 sets at azimuth 64° around 08:58.
Steve M
CODE
Date__(UT)__HR:MN R.A._(ICRF/J2000.0)_DEC Azi_(a-appr)_Elev APmag delta deldot
2008-Jan-30 08:46 *x 00 27 42.40 +04 09 49.2 62.7359 6.6904 11.84 .000362743392784 -3.6132119
2008-Jan-30 08:47 *x 00 30 26.68 +04 31 02.6 62.8366 6.1478 11.79 .000361326476080 -3.4514578
2008-Jan-30 08:48 *x 00 33 12.37 +04 52 23.2 62.9406 5.5997 11.74 .000359974811601 -3.2878687
2008-Jan-30 08:49 *x 00 35 59.44 +05 13 50.6 63.0478 5.0466 11.70 .000358689122027 -3.1225070
2008-Jan-30 08:50 *x 00 38 47.87 +05 35 24.0 63.1582 4.4885 11.65 .000357470106030 -2.9554397
2008-Jan-30 08:51 *x 00 41 37.61 +05 57 03.0 63.2719 3.9258 11.61 .000356318432869 -2.7867378
2008-Jan-30 08:52 *x 00 44 28.63 +06 18 46.6 63.3888 3.3586 11.56 .000355234743186 -2.6164768
2008-Jan-30 08:53 *x 00 47 20.89 +06 40 34.4 63.5089 2.7874 11.52 .000354219647010 -2.4447365
2008-Jan-30 08:54 *x 00 50 14.35 +07 02 25.5 63.6323 2.2123 11.48 .000353273720220 -2.2716007
2008-Jan-30 08:55 *x 00 53 08.98 +07 24 19.2 63.7588 1.6337 11.44 .000352397505902 -2.0971568
2008-Jan-30 08:56 *x 00 56 04.71 +07 46 14.8 63.8885 1.0518 11.40 .000351591509798 -1.9214965
2008-Jan-30 08:57 *x 00 59 01.52 +08 08 11.5 64.0213 0.4669 11.36 .000350856200915 -1.7447145
2008-Jan-30 08:58 *s 01 01 59.34 +08 30 08.5 64.1573 -0.1206 11.32 .000350192009932 -1.5669092
2008-Jan-30 08:59 *x 01 04 58.13 +08 52 05.1 64.2965 -0.7104 11.28 .000349599326403 -1.3881819
2008-Jan-30 09:00 *x 01 07 57.84 +09 14 00.3 64.4386 -1.3022 11.24 .000349078499932 -1.2086367
2008-Jan-30 09:01 *x 01 10 58.40 +09 35 53.5 64.5839 -1.8956 11.20 .000348629836515 -1.0283802
2008-Jan-30 09:02 *x 01 13 59.77 +09 57 43.8 64.7322 -2.4903 11.17 .000348253600287 -0.8475213
2008-Jan-30 09:03 *x 01 17 01.89 +10 19 30.3 64.8835 -3.0860 11.13 .000347950010097 -0.6661708
2008-Jan-30 09:04 *x 01 20 04.69 +10 41 12.3 65.0378 -3.6823 11.10 .000347719240611 -0.4844409
2008-Jan-30 08:46 *x 00 27 42.40 +04 09 49.2 62.7359 6.6904 11.84 .000362743392784 -3.6132119
2008-Jan-30 08:47 *x 00 30 26.68 +04 31 02.6 62.8366 6.1478 11.79 .000361326476080 -3.4514578
2008-Jan-30 08:48 *x 00 33 12.37 +04 52 23.2 62.9406 5.5997 11.74 .000359974811601 -3.2878687
2008-Jan-30 08:49 *x 00 35 59.44 +05 13 50.6 63.0478 5.0466 11.70 .000358689122027 -3.1225070
2008-Jan-30 08:50 *x 00 38 47.87 +05 35 24.0 63.1582 4.4885 11.65 .000357470106030 -2.9554397
2008-Jan-30 08:51 *x 00 41 37.61 +05 57 03.0 63.2719 3.9258 11.61 .000356318432869 -2.7867378
2008-Jan-30 08:52 *x 00 44 28.63 +06 18 46.6 63.3888 3.3586 11.56 .000355234743186 -2.6164768
2008-Jan-30 08:53 *x 00 47 20.89 +06 40 34.4 63.5089 2.7874 11.52 .000354219647010 -2.4447365
2008-Jan-30 08:54 *x 00 50 14.35 +07 02 25.5 63.6323 2.2123 11.48 .000353273720220 -2.2716007
2008-Jan-30 08:55 *x 00 53 08.98 +07 24 19.2 63.7588 1.6337 11.44 .000352397505902 -2.0971568
2008-Jan-30 08:56 *x 00 56 04.71 +07 46 14.8 63.8885 1.0518 11.40 .000351591509798 -1.9214965
2008-Jan-30 08:57 *x 00 59 01.52 +08 08 11.5 64.0213 0.4669 11.36 .000350856200915 -1.7447145
2008-Jan-30 08:58 *s 01 01 59.34 +08 30 08.5 64.1573 -0.1206 11.32 .000350192009932 -1.5669092
2008-Jan-30 08:59 *x 01 04 58.13 +08 52 05.1 64.2965 -0.7104 11.28 .000349599326403 -1.3881819
2008-Jan-30 09:00 *x 01 07 57.84 +09 14 00.3 64.4386 -1.3022 11.24 .000349078499932 -1.2086367
2008-Jan-30 09:01 *x 01 10 58.40 +09 35 53.5 64.5839 -1.8956 11.20 .000348629836515 -1.0283802
2008-Jan-30 09:02 *x 01 13 59.77 +09 57 43.8 64.7322 -2.4903 11.17 .000348253600287 -0.8475213
2008-Jan-30 09:03 *x 01 17 01.89 +10 19 30.3 64.8835 -3.0860 11.13 .000347950010097 -0.6661708
2008-Jan-30 09:04 *x 01 20 04.69 +10 41 12.3 65.0378 -3.6823 11.10 .000347719240611 -0.4844409
Asteroid 2007 WD5 sets at azimuth 64° around 08:58.
Steve M
Forget it with Spirit - no where near enough power to get up early or stay up late to observe something like this. The best instruments would be OpNav, Marci or CTX on MRO.
Doug
Doug
Anyway at those odds it won't probably happen and even if it did, it won't be visible for ground-based obseevatories: http://www.badastronomy.com/bablog/
Yeah, 1 in 75 isn't great...but here's hoping for some serious luck!!! We have 3 active orbiters; there's never been a better time in history for this to happen!
I'm not as interested in seeing the actual impact itself as I am in seeing the resultant crater, which would be strong enough to expose some deeply buried materials that could be studied before the ubiquitous dust coats them...
I'm not as interested in seeing the actual impact itself as I am in seeing the resultant crater, which would be strong enough to expose some deeply buried materials that could be studied before the ubiquitous dust coats them...
QUOTE (djellison @ Dec 21 2007, 04:05 AM) 
Forget it with Spirit - no where near enough power to get up early or stay up late to observe something like this. The best instruments would be OpNav, Marci or CTX on MRO.
Doug
Doug
Agreed, and with an apparent magnitude of around 11.5, it would be pushing the limits of the rovers even at their prime. Of course, if it came a bit closer it would be somewhat brighter, and if it impacted it would get very bright.
Steve M
The ephemeris is likely to change, as it's only based on 25 observations spanning 29 days.
Steve M
Steve M
QUOTE (nprev @ Dec 21 2007, 04:07 AM)
I'm not as interested in seeing the actual impact itself as I am in seeing the resultant crater, which would be strong enough to expose some deeply buried materials that could be studied before the ubiquitous dust coats them...
I guess that would open up another round of MSL landing site discussions wouldn't it?
QUOTE (nprev @ Dec 21 2007, 07:07 AM)
... the resultant crater, which would be strong enough to expose some deeply buried materials...
Maybe an ice/water table! Imagine a crater filling with boiling, steaming water!
100 meter diameter 5000 kilometers away. Any camera gurus here that can convert that into pixels for the various cameras available out Mars way?
HiRise would certainly be able to take a detailed image but unfortunately the pointing problems are probably prohibitive, even though there will certainly be a rush of new observations to improve the ephemeris.
HiRise would certainly be able to take a detailed image but unfortunately the pointing problems are probably prohibitive, even though there will certainly be a rush of new observations to improve the ephemeris.
SS at space.com:
"“If an impact takes place, the most likely thing for us to observe would be dust that has been lofted into the atmosphere by the impact event and then carried over the rover sites by wind,” Squyres said. “So if there is an impact, we’ll increase our monitoring of dust in the atmosphere to see if we can observe any effects.”
"Squyres added that the rover team, of course, would try to image the sky at the predicted time of impact to see if anything can be seen, “but that’s got to be considered a very improbable long shot.”
"“If an impact takes place, the most likely thing for us to observe would be dust that has been lofted into the atmosphere by the impact event and then carried over the rover sites by wind,” Squyres said. “So if there is an impact, we’ll increase our monitoring of dust in the atmosphere to see if we can observe any effects.”
"Squyres added that the rover team, of course, would try to image the sky at the predicted time of impact to see if anything can be seen, “but that’s got to be considered a very improbable long shot.”
HiRISE - ROUGHLY - does something like distance in km / 10 = cm/pixel (i.e. 250km=25cm - 300km=30cm) - so 5000km = 5m/pixel - 20 pixels across.
CTX is 20 x that, so 100m/pixel - one pixel - and very roughly speaking, the same for THEMIS and HRSC.
Doug
CTX is 20 x that, so 100m/pixel - one pixel - and very roughly speaking, the same for THEMIS and HRSC.
Doug
.
Ooo...neat idea! Couple of hurdles, though:
1. Have to know the impact time quite precisely (and right now, odds are that it ain't even gonna hit).
2. Need to use the DTE link for the entire window to both catch the hit & establish a baseline to derive variations.
3. The carrier freq won't be affected by the impact, only (potentially) the antenna pointing accuracy, which would presumably experience variations in received dBm's from vibration & consequent small pointing errors. Don't know if these would be significant enough to notice, unless it hits very close to one of the MERs.
While writing this, had another idea: Do the MERs have load cells or any other method of monitoring wheel weight loads or static axial torsion? If so, and if the impact generates a detectable seismic event, then variations in this telemetry might provide the same sort of data.
1. Have to know the impact time quite precisely (and right now, odds are that it ain't even gonna hit).
2. Need to use the DTE link for the entire window to both catch the hit & establish a baseline to derive variations.
3. The carrier freq won't be affected by the impact, only (potentially) the antenna pointing accuracy, which would presumably experience variations in received dBm's from vibration & consequent small pointing errors. Don't know if these would be significant enough to notice, unless it hits very close to one of the MERs.
While writing this, had another idea: Do the MERs have load cells or any other method of monitoring wheel weight loads or static axial torsion? If so, and if the impact generates a detectable seismic event, then variations in this telemetry might provide the same sort of data.
Ahhh for a couple [three please?] of seismometers on the ground! 
I still think its a damn shame that the Viking [2?] instrument didn't uncage...
P
I still think its a damn shame that the Viking [2?] instrument didn't uncage...
P
I think would need a dedicated seismometer on the rover to get any useful scientific data. Sure, you might be able to come up with some method to detected some sort of shake, rattle and roll. But really...how useful would such a detection be? Wouldn't we need something a bit more sensitive? Don't you need something to compare data with here on Earth to make any sense of it? If such a makeshift method would work, why hasn't the MER team created one already to detect possible Marsquakes?
I'm skeptical. But I hope you guys can prove my skeptism unfounded. I love the discussion about the possibility! I guess it is OK to dream about it.
I'm skeptical. But I hope you guys can prove my skeptism unfounded. I love the discussion about the possibility! I guess it is OK to dream about it.
Obviously, it's a long shot for it to hit Mars at all, but if it does, the extra-exciting longshot would be that one of the rovers would be inside the debris apron, and we could identify the new baubles by comparing the image to the day before. Then, in good time, drive over and examine them.
Somebody ask Santa nicely for this!
Somebody ask Santa nicely for this!
I think that a nice, deep hit dead square on Meridiani is on all our Christmas lists, a few kilometers from Oppy (who would, in this perfect scenario, be well sheltered from any ill effects inside Victoria...)
.
.
QUOTE (nprev @ Dec 21 2007, 04:55 PM)
I think that a nice, deep hit dead square on Meridiani is on all our Christmas lists, a few kilometers from Oppy (who would, in this perfect scenario, be well sheltered from any ill effects inside Victoria...)
Careful what you wish for... A few kilometers might not be enough to protect Oppy, even in Victoria. If you look at images (MOC and HiRISE) of very recent Mars impact craters detected from orbit, visible scouring effects extend for at least 10 crater diameters, and ground-hugging impact surge clouds composed mainly of dust could therefore reach at least that far, bowling Oppy over, or at the very least, coating its solar cells with dust and sand. Surge deposit accumulations should be thicker than usual inside a crater, although the surge cloud might have enough internal energy to climb the far side and keep going (original dip - deposition as inclined beds - is common in surge deposits, such as those at Home Plate, that may have overridden an old impact crater or other small bowl shaped depression).
But what I wouldn't give for some nice pancam and orbital images of the dust storm-like impact surge cloud rapidly advancing across Meridiani Planum towards Oppy! Of course, that still wouldn't convince the doubters...
-- HDP Don
QUOTE (dburt @ Dec 21 2007, 06:00 PM)
Of course, that still wouldn't convince the doubters...
Not until we witnessed freshly created hematite spheres raining from your impact surge cloud.
QUOTE
Obviously, it's a long shot for it to hit Mars at all, but if it does, the extra-exciting longshot would be that one of the rovers would be inside the debris apron, and we could identify the new baubles by comparing the image to the day before. Then, in good time, drive over and examine them.
Somebody ask Santa nicely for this!
Somebody ask Santa nicely for this!
I dont think I would feel comfortable for Oppy or Spirit to be that close to ground zero
. But on the other hand, it would certinly look cool on pancam, if it survives stuff falling from the sky .
If the astroid does impact near atleased one rover, I prefer it to be Spirit. Speeking of which, in the extreamly thin martian atmosphere, and an impactor of this size, and the speed at which the astroid is traveling, how powerfull would the over pressures be at impact?. With a fairly moderate or even gentle blast wave, Im positive that would clear spirit's dusty solar panels .
.
It would great to have a new impact crater carved, so we could send the Mars Science Laboratory to that! Let's hope that, if it hits Mars, it will impact somewhere that permits EDL for MSL.
As for Opportunity, a debris cloud in the higher atmosphere will be just one more thing to weather on her epic journey...
As for Opportunity, a debris cloud in the higher atmosphere will be just one more thing to weather on her epic journey...
JPL's Near Earth Object Program has a good report on 2007 WD5 with a lot of useful links and figures. It says that
Especially interesting is an animation showing the intersection of the asteroid's uncertainty elipsoid with Mars. With future observations the uncertainty elipsoid will get smaller and may move.
Steve M
QUOTE
The uncertainty region during the Mars encounter currently extends over a million kilometers (700,000 miles) along a very slender ellipsoid only 1200 km (700 miles) wide, but the ellipsoid does intersect Mars. The zone of potential impact on the surface of Mars is approximately 800 km wide, and sweeps across the Martian equator from southwest to northeast, crossing the equator at roughly 30 deg W longitude. The MER Opportunity rover is close to the southern edge of this possible impact zone but clearly outside it.
Especially interesting is an animation showing the intersection of the asteroid's uncertainty elipsoid with Mars. With future observations the uncertainty elipsoid will get smaller and may move.
Steve M
"Squyres added that the rover team, of course, would try to image the sky at the predicted time of impact to see if anything can be seen, “but that’s got to be considered a very improbable long shot.”
[/quote]
This is amazing! I would hope an actual impact could be recorded by one or more of the orbiters if line of sight considerations work out . A series of frames shot in as rapid a sequence as possible for an 'animation' would be useful to document the ejecta plume as it spreads from the impact point.
Some of the very fresh impact craters on Mars are surrounded by ray patterns bearing signs of fine material near the crater being prevented from reaching the ground, then at a certain radius outwards appearing very much like Lunar crater rays in negative. This may be due to the innermost ejecta cone being disrupted by nearby inward rushing winds filling the column of air evacuated by the shock wave, as well as later winds feeding the rising 'mushroom cloud'. What a thing that would be to observe!
If it were possible to observe a fortuitous (but distant!) impact with a rover, especially a future one with a true video capability, so much the better.
Don
[/quote]
This is amazing! I would hope an actual impact could be recorded by one or more of the orbiters if line of sight considerations work out . A series of frames shot in as rapid a sequence as possible for an 'animation' would be useful to document the ejecta plume as it spreads from the impact point.
Some of the very fresh impact craters on Mars are surrounded by ray patterns bearing signs of fine material near the crater being prevented from reaching the ground, then at a certain radius outwards appearing very much like Lunar crater rays in negative. This may be due to the innermost ejecta cone being disrupted by nearby inward rushing winds filling the column of air evacuated by the shock wave, as well as later winds feeding the rising 'mushroom cloud'. What a thing that would be to observe!
If it were possible to observe a fortuitous (but distant!) impact with a rover, especially a future one with a true video capability, so much the better.
Don
I like it!
Awesome thought; awesome image, Stu! Thanks!!!
QUOTE (Stu @ Dec 22 2007, 11:51 PM)
Well, we can dream, eh..?
I was thinking about something on the lines of this:Click to view attachment
*sigh* If only...
It had not occurred to me before, but it seems like the MER rovers' inertial navigation system might double as a seismometer. Completely aside from recording this impact, this strikes me as a useful capability.
The resolution and sensitivity of the IMU's is almost certainly several orders of magnitude short of what would be required to detect a distant impact or any seismic activity.
Doug
Doug
My recollection is that running the IMU burns a lot of energy (relatively speaking), so it is probably not practical to keep it running for any great length of time. On the other hand, both rovers are sitting on bedrock at the moment, so if the sensitivity exists they're in a good position to take advantage of it. Pure speculation - I have no idea what the specs on the accelerometers are, nor whether the computer can access them in isolation from the IMU system.
Are they ring-laser gyro IMUs, or are they mechanical? Makes a big difference in power requirements, also sensitivity. Most modern intertial nav systems can detect accelerations of a few thousandths of a g, which is why they're now integral for autopilots.
This is a great idea, AG; as long as the MERs are stationary at the time of impact (allowing for propagation time) they should be able to detect some sort of shock. (I didn't know that the MERs even HAD IMUs...)
This is a great idea, AG; as long as the MERs are stationary at the time of impact (allowing for propagation time) they should be able to detect some sort of shock. (I didn't know that the MERs even HAD IMUs...)
Could you use a Pancam image of a bright star at night to record shaking due to impact?
Would the image jiggle be enough to tell you how much the rover felt?
-Mike
Would the image jiggle be enough to tell you how much the rover felt?
-Mike
QUOTE (nprev @ Dec 23 2007, 02:05 AM)
Are they ring-laser gyro IMUs, or are they mechanical?
The MERs use the popular LN-200 IMU. Full specs here:
http://www.nsd.es.northropgrumman.com/Auto...cts/LN-200.html
You know... don't get me wrong, guys, but, um... one in 75 is still pretty big odds against something happening.
I'm seeing people getting real excited over something that is more than likely not going to happen.
Let's not get ourselves all het up over it and then get all upset when it doesn't happen, okay, folks?
-the other Doug
I'm seeing people getting real excited over something that is more than likely not going to happen.
Let's not get ourselves all het up over it and then get all upset when it doesn't happen, okay, folks?
-the other Doug
Aw, other Doug, it's all part of the fun! 1/75 is rubbish odds, I know, but it's fun to speculate. Heck, we've spent weeks before speculating on such things as the location and nature of "Beacon" etc. It's Christmas, let's play a little.
3 new (old) observations from Apache Point-Sloan Digital Sky Survey have been added to the arc, extending it back to 2007/11/08. I think JPL Horizons has an updated ephemeris, since it now shows closest approach at 2008-Jan-30 11:45 at a distance of 21,006 km from the center of Mars, down from the previous 51,722 km closest approach. This may or may not actually mean the chances of impact went up, but either way I can't wait to hear what the impact gurus have to say.
Perhaps counterintuitively, these new observations might actually rule out an impact, despite the closer projected approach distance. How wide was the across-track uncertainty prior to this observation? Looking at SteveM's animation, it was huge. If the uncertainty now is less than +/- 21000 km the deal's off.
This would be truly a once in a lifetime event, but really, the odds are strongly against it.
This would be truly a once in a lifetime event, but really, the odds are strongly against it.
The cone of uncertainty from a couple of days ago extended over a million kilometers (700,000 miles) along a very slender ellipsoid only 1200 km (700 miles) wide. That's why they could say with certainty that Opportunity was safe. They knew where on Mars the asteroid could possibly hit.
I don't know the exact figures altered by these new earlier observations added to the equations, but my best guess is that Mars is still very much within the cone of uncertainty. And if that is true, then the odds of a hit just went dramatically up. The predicted path keeps getting closer and closer to Mars. First is was around 100,000 km; then it was 50,000 km; and now it is 21,000 km. Do you see the trend? The cone of uncertainty is too wide of a swath for it not to be still intersecting with Mars. Yet, how much of the cone is current filled by Mars determines the actual odds of a strike. I'd like to see the new figures in detail.
We still won't be able to rule out an impact on Mars until a couple of weeks with new, fresh observations of the asteroid.
I don't know the exact figures altered by these new earlier observations added to the equations, but my best guess is that Mars is still very much within the cone of uncertainty. And if that is true, then the odds of a hit just went dramatically up. The predicted path keeps getting closer and closer to Mars. First is was around 100,000 km; then it was 50,000 km; and now it is 21,000 km. Do you see the trend? The cone of uncertainty is too wide of a swath for it not to be still intersecting with Mars. Yet, how much of the cone is current filled by Mars determines the actual odds of a strike. I'd like to see the new figures in detail.
We still won't be able to rule out an impact on Mars until a couple of weeks with new, fresh observations of the asteroid.
QUOTE (MarsIsImportant @ Dec 23 2007, 06:05 PM)
We still won't be able to rule out an impact on Mars until a couple of weeks with new, fresh observations of the asteroid.
I'm a pessimist so I'll formulate it this way: we still won't be able to rule out a miss until new observations show up. The fact the predicted path is getting closer to Mars isn't really indicative of anything, it could miss ("overshoot") Mars and go to the other side just as well for all we know. Mars is not some kind of a great attractor here!
Remember back when Apophis (?) was tracked for an Earth impact, there was a slight increase of a chance for a hit at one point only to be ruled out by later measurements. The predicted path is just one point in a large ellipse, not the most probable point at that.
I'm looking forward to new probability estimates and ellipses, but even a 10-fold decrease (probably unlikely with only 3 recently added datapoints) in ellipse semimajor axis still leaves a whopping 100 000 km impact parameter.
Mars has gravity. And the current best guess path takes it to only within 2 and 1/2 times the the diameter of Mars to an actual impact. That is extremely close. The closer it gets to Mars, the more Mars' gravity will affect the path of the asteroid. So the trend is significant, because we need to know where this thing is going to go. Afterall, this is a NEO too.
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