Mars Comet Encounter Observations, C/2013 A1 Siding Spring, 19 Oct 2014 Options

[fredk]

Here's a very quick and dirty attempt at stacking 8 of the press release mastcam images:

I've done a 2pix Gaussian blur to reduce noise. Definitely some coma visible.

[CPAero]

Hi all, long time reader and big fan of all the image processing and discussion that goes on in these forums. I haven't yet found a treatment of the following sequence of MSL M100 sub-frames in these forums or elsewhere, and I would love to see what you guys/gals can do with this set. The comet is first visible in 0783MR003377 at row 282, col 565, and scoots toward lower right in successive frames. Forgive me if this sequence has already been discussed.

0783MR0033770000204176E01_DXXX.jpg
0783MR0033780020204180E01_DXXX.jpg
0783MR0033790000204182E01_DXXX.jpg
0783MR0033800000204184E01_DXXX.jpg
0783MR0033810020204188E01_DXXX.jpg
0783MR0033820000204190E01_DXXX.jpg
0783MR0033830000204192E01_DXXX.jpg
0783MR0033840020204196E01_DXXX.jpg

Cheers
-Ryan

[nprev]

Apparently there may have been quite a meteor shower associated with passage of the comet. Unfortunately, the rovers aren't equipped to observe such an event:

http://www.nytimes.com/2014/11/08/science/...n-sky.html?_r=0

[Explorer1]

Yes, it was mentioned in the telecon this morning, along with a possible bright yellow glow in the night sky (from the sodium in the coma). The human eye would be far more subtle a detector than any mechanical camera, they mentioned.

[Gerald]

The comet is first visible in 0783MR003377 at row 282, col 565, and scoots toward lower right in successive frames.

That's the only moving object visible without image processing. Difficult to see in a single raw image. But it's not the comet, it's Izar, the bright streak in the released processed MC images.
The comet is really subtle, maybe even more subtle than 34 W Boötis, which can be made visible, too.

[fredk]

Yes, it was mentioned in the telecon this morning

I heard part of that but there seemed to be contradictory statements - someone said it would've been a spectacular show from the ground, but I thought someone also said the meteor particle sizes would've been very tiny, like dust, so you may not have seen many meteors. In other words, there was lots of fine dust coming in, rather than particles of typical naked-eye meteor size on Earth. Did anyone get a clearer picure of this from the conference?

Either way, I was surprized that they saw such an obvious effect in terms of ionized metals etc.

[MahFL]

...so you may not have seen many meteors.

They said you may have seen 1000's of meteors per hour, for about 90 minutes. 1000's....

[elakdawalla]

That was one of the bits of the conference where there may have been a little disagreement on the panel. It was Nick Schneider saying there would've been a couple of tons of material entering Mars' atmosphere, which would result in a 1000s of meteors per hour storm. I forget who commented later about the particle size being smaller.

[Deimos]

If the 1-3 mm size predictions were right (http://cometcampaign.org/tony/orbiter-results), the 'storm' would have produced a lot of meteors bright enough for normal human vision in dark skies, and many could have been bright enough for one of the rovers to see (in dark skies). If it had been partitioned into 1 g chunks, the rovers' cameras could have seen 1 every few minutes. If smaller, then it could have been human-visible but not visible to the current rover cameras (that's one area the sensitivities are not similar). But of course the prime reasons the rovers couldn't have seen it are not instrumental: daylight and (for MSL) 1000s of km of Mars.

Given the high speeds, the meteors might have become daytime visible (to a person) at a few grams, but short exposure times would have meant that 1000s of images would be needed to see one in a Pancam image--not to mention skipping the comet images. If close approach had been during the time Opportunity actually took images, there might have been not only a streaking comet, but 'noctilucent' illuminated trails left behind the meteors. But again, much smaller than this is expected for comet dust.

[TheAnt]

I was going to add some tidbits to the meteor matter, but Deimos beat me to it.
I link this link for anyone who like to read up though.

[Reed]

Somewhat related, Mars Express had observations dedicated to meteor hunting, see pages 7-8 of http://mars.nasa.gov/files/mep/sidingsprin...tions_WebEx.pdf

Since nothing from this showed up in their first image release, it seems like a safe bet they didn't get anything spectacular.

[Explorer1]

Without any atmosphere, Phobos and Deimos probably got a light peppering too. Would any craters even be more than a few cm across, or are they more like when tiny flecks of space junk do damage in LEO (i.e. microscopic)?

[tolis]

Without any atmosphere, Phobos and Deimos probably got a light peppering too. Would any craters even be more than a few cm across, or are they more like when tiny flecks of space junk do damage in LEO (i.e. microscopic)?

Good question. starting from Tony Farnham's 0.1 (1-3mm-sized) grains per sq km per hour and assuming that Phobos (Deimos) would present a disk
of surface area of 400 (100) sq km to the flux, one arrives at figures of 40 (10) particle impacts per hour. If the ratio of crater size to particle size
is taken to be ~20, that gives you crater sizes in the range 1 cm to 6 cm. I doubt these can be discerned by anything other than a lander
(and you would also need before-and-after shots which you don't have anyway). Another aspect of this is the amount of mass lifted by those impacts
and going into orbit around Mars: if the yield (the ratio of ejecta mass to impactor mass) is ~1000 (this is a notorious fudge factor, by the way) and all of it escapes the moon's gravity, you end up with 40x1000x(a 10 milligram impactor) = 400 grams for phobos. so, more mass than an orange but less than a melon.

[nprev]

Great analysis, tolis, thanks! Doesn't sound like any detectable consequences at all, then.

However, the 'hide-the-orbiters' strategy still seems to have been a very prudent move. The odds of damage were pretty low, but definitely well above zero.

[tedstryk]

My latest blog post is largely based on the Hubble observations at the time of the climate flyby. It is unusual for it to look at Mars when it is so far away.