2
$\begingroup$

The abstract of the open access 2014 paper Meteor hurricane at Mars on 2014 October 19 from comet C/2013 A1 says:

omet C/2013 A1 will make a very close approach with the planet Mars on 2014 October 19. For this event, we compute the density of cometary dust particles around the Mars Express spacecraft, in order to assess the real risk for space probes. We also estimate the zenithal hourly rate (ZHR) and discuss observational opportunities for the resulting Martian meteor shower. We find, for a surface of 2.7  m2, that the Mars Express spacecraft will experience approximately 10 impacts from particles larger than 100 μm in size. The fluence per square metre is found to be 3.5 during the encounter. The equivalent ZHR is computed to be ZHR ≃ 4.75 × 109 h−1, making this event the strongest meteor storm ever predicted. We call this event a ‘meteor hurricane’, which we define to be a meteor shower with ZHR exceeding 106 h−1. The event will last approximately 5 h in total, and peak around 20:00 UT (Earth UT time). We call for observations of this unique event by all possible means, but also warn operators of Mars-orbiting spacecraft against the risks of impacts from comet particles larger than 100 μm, with impacts speeds of 57.42 km s−1.

The paper warns operators of Mars-orbiting spacecraft of a "meteor hurricane" and estimates the real possibility of Mars Express getting hit by a 100 μm particle at 57 km/s.

It also suggests that folks watch for this event "by all possible means".

Question(s):

  1. Did Mars Express get hit by a "Meteor hurricane"? (2014 October 19, comet C/2013 A1) Were any impacts detected at all during this timeframe?
  2. Was the observed at all "by all possible means"? For example did any rover try to look for meteors at dusk while the sky darkened but they were still warm enough to operate? Did any orbiting spacecraft look down on the night side for fireballs?
$\endgroup$
2
  • 1
    $\begingroup$ Was the paper authored by Little, Chicken? $\endgroup$ Apr 23, 2021 at 3:53
  • $\begingroup$ hmmm. 100 μm particle at 57 km/s contains about the energy of a .22 short subsonic round, about 65 Joule. It will make a nice impact crater in whatever it hits, but will not penetrate anything, not even a single layer of mylar, without vaporizing itself spectacularly. This is actually a believable threat, if the density/chance of impact becomes high enough. The problem is that 57km/s. It is a ludicrously unlikely confluence of a fast comet meeting a planet head-on in the planet's orbit. $\endgroup$ Apr 23, 2021 at 10:35

1 Answer 1

4
$\begingroup$

Crismani et al (2018). "The Impact of Comet Siding Spring’s Meteors on the Martian Atmosphere and Ionosphere" Journal of Geophysical Research: Planets.

... we show this shower lasted less than 3 hr and was therefore limited to one hemisphere. Meteoric ablation occurred in a narrow altitude layer, with Mg+, Mg, Fe+, and Fe deposited between about 105 and 120 km, consistent with comet Siding Spring's relative velocity of 56 km/s. We find that 82 ± 25 t of dust was deposited, improving previous measurements and a thousand times larger than model expectations.

Assuming a clear sky for an observer at the surface of Mars, with similar assumptions to Schneider et al. (2015), we revise the expected zenithal hourly rate to 5 × 10^5 meteors per hour, or 160 meteors per second.

The projections in Vaubaillon et al seemed to be significantly higher than this, with a ZHR of 10^8 to 10^9 meteors per hour and 10^7 kg of deposited material. However, some other predictions had suggested that it would deposit less than 100kg of material, and be virtually unnoticeable - there was a very wide range involved. This particular prediction was definitely too high, but the event was probably closer to the "serious storm" level than "nothing noticeable". The definition of "meteor hurricane" they proposed is 10^6 meteors per hour - so it did come close to that threshold.

And finally, it wasn't directly viewed:

The Martian rovers would not have been able to observe this event however, since Opportunity was already in daylight and Curiosity was on the shielded hemisphere. Very bright fireballs may have been visible in the daylight; however, these make a small fraction of the overall meteor shower and it is unclear whether these would have been detected. Similarly, orbiting spacecraft were intentionally attempting to hide from this event, and we are unaware of any images of the planet or atmosphere that were taken during comet Siding Spring's closest approach.

The lack of direct impacts on Mars Express was probably due to the overall flux being about four orders of magnitude less than the highest projections, which turns "a decent chance of being hit by ten particles" into "about a one percent chance of being hit by any".

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.