The meteoroid fluence at Mars due to Comet C/2013 A1 ... McNaught 0.5 meter telescope Siding Spring,...

The meteoroid fluence at Mars due toComet C/2013 A1 (Siding Spring)

Althea MoorheadNASA Meteoroid Environment Office

Collaborators:Paul Wiegert (UWO) & Bill CookeRhiannon Blaauw & Aaron Kingery

Will Yoder & Cameron McCarty

May 2, 2014

https://ntrs.nasa.gov/search.jsp?R=20140010989 2018-06-06T19:57:06+00:00Z

On October 19, 2014, Comet C/2013 A1 (Siding Spring)will pass within 150,000 km of Mars.

This is closer than all known Earth-comet encounters.

A collision has been ruled out, but Mars and its manmadesatellites will pass through the coma and tail.

Mars will be showered with meteors and satellites willhave an increased risk of meteoroid impacts.

http://www.minorplanetcenter.net/iau/lists/ClosestComets.html

Comet backgroundComa model

Recent observations

Outline

1 Comet backgroundC/2013 A1 (Siding Spring)Mars encounterMars spacecraft

2 Coma modelAnalytic modelValidation and simulationsEffects at Mars

3 Recent observationsBrightness monitoringObservational constraintsComparison with Hale-Bopp

Moorhead Siding Spring at Mars 3/ 38


Recent observations

C/2013 A1 (Siding Spring)Mars encounterMars spacecraft

Comet types: classed by orbit

Type Orbit Origin Examples

Short period P < 200 yrs Kuiper Belt Halley

Long period(Oort cloud)

P ∼ 1000s yrs Oort cloudHale-Bopp,C/2013 A1

SungrazersPass near or plunge intothe Sun

C/2012 S1 (ISON)



Recent observations


Comet properties

Comet Hartley 2

Comets are the leastreflective objects in theSolar System:

Halley has an albedo ofabout 4%.Asphalt has a albedo of7%.

Long period cometscontain more volatiles, asshort period comets losemuch of these in frequentpassages around the Sun.



Recent observations


Cometary comae

Comet Hale-Bopp, NASA

Hale-Bopp:

Discovered at 7.2 AUComa was 1 million kmin August 1995

Siding Spring:

Imaged at 10 AUAlready active



Recent observations


C/2013 A1 (Siding Spring)

Discovery:

January 3, 2013Rob McNaught0.5 meter telescopeSiding Spring, Australia

Pre-discovery imageslocated in Catalina SkySurvey

Active in earliest images(Dec. 8, 2012)

Hyperbolic orbit


Ima

ge

cred

it:

NA

SA

/JP

L


Recent observations


Close encounter with mars

Movie credit: Leonid Elenin using SpaceEngine software



Recent observations


Close encounter with mars

Comet is north ofMars’s orbital plane atclosest approach

Close approach:131,000 - 145,000 km

Approach distancenominal value:138,000 km

Coma/tail may envelopMars



Recent observations


Mars satellites

Odyssey (NASA)400 km, 2 hr orbit

MRO (NASA)300 km, 2 hr orbit

Mars Express (ESA)300 - 10,000 km

7.5 hr orbit

MAVEN (NASA)150 - 6,200 km, 4.5 hr orbit

Arrives September 2014

MOM (ISRO)365 - 80,000 km, 76.7 hr orbit

Arrives September 2014



Recent observations


Meteoroid impact risks

Impacts to critical components

Sudden attitude changes

Electrostatic/EMP effects may occur, depending onenvironment and spacecraft charging state

Image courtesy of MEDUSSA


http://sess.stanford.edu/medussa


Recent observations



Encounter speed similarto Perseids at Earth

Two spacecraft anomaliesattributed to Perseids:

Landsat 5 lost attitudecontrol during 2009PerseidsOLYMPUS satellitelost during 1993Perseids

Image from McDonnell et al., 1993


http://www.astronomy.com/en/News-Observing/News/2005/06/Deep%20Perseid%20impact.aspx

http://www.astronomy.com/en/News-Observing/News/2005/06/Deep%20Perseid%20impact.aspx


Recent observations


Possible mitigation strategies

Align solar arrays sunward, edge-on to meteor shower

Sun-Mars-comet angle is 90.2◦

Present hard side to radiant

Phase orbit to use Mars as a partial shield:

Depends on orbit geometryShower will last a few hours, dependent on coma size(30 min per 100,000 km of coma/tail)Odyssey and MRO have 2 hour orbits



Recent observations

Analytic modelValidation and simulationsEffects at Mars

Particles in the coma and tail of Siding Spring

Coma and tail contains both gasand particles

Both grow as heliocentric distancedecreases

Fluence – flux integrated overMars/spacecraft trajectory

Direct measure of spacecraft risk

We compute the particle fluence atMars using properties of SidingSpring (magnitude, orbit),supplementing with Halley data(particle albedo, size distribution)where necessary.



Recent observations


The Giotto flyby of 1P/Halley

We have detailed coma data forone comet: Halley.

Giotto recorded 12,000 impacts.

Model fits to these data yield:

Particle density and albedoParticle size distributionParticle spatial distribution

Total number of particlesderived from Siding Springmagnitude, not Halley.



Recent observations


Analytic model

Quantifying the number of ∼100 micron1 or larger particles in thecoma/tail:

1 Determine the brightness at the time of the encounter.

2 Use particle albedo to compute the total particle surface area.

3 Combine with Halley-like particle size distribution andmaterial density to compute number of particles.

4 Use r−2 spatial distribution to compute the number density.

5 Integrate along the trajectory to get fluence.

Our analytic model can be used to quickly calculate new fluenceestimates as comet properties are measured/constrained.

1100 micron particles are capable of cutting exposed spacecraft wires. Masslimit is 4× 10−6 g, actual size limit depends on density



Recent observations


Analytic model

σ∗ =gh−β

a

(2

π

) 13 (ρ

3

) 23

10−0.4(M1−m�,1au) au2

×(

3− k

1− k

)(m

(1−k)/3max −m

(1−k)/3∗

m(3−k)/3max −m

(3−k)/3min

)

×cos−1(b/rc)

b rc



Recent observations


Analytic modelDependence on comet/meteoroid properties

7 8 9 10

0.01

0.1

comet magnitude)

Flu

ence

(m−

2)

0.01 0.02 0.04 0.08

0.01

0.02

0.03

0.04

albedo(

0.01 0.1 10

0.02

0.04

bulk density (g/cc)

Flu

ence

(m−

2)

1 2 4

0

00.1

0.2

0.3

0.4

size index(



Recent observations


Analytic modelFluence depends strongly on close approach distance

0 50 100 150 200 250 300

0.001

0.01

0.1

1

10

Close approach distance (103 km)

Tot

alfl

uen

ce(m

−2)

Coma Radius300,000 km250,000 km200,000 km150,000 km100,000 km

50,000 km

138 000 km

0.011 m−2 fluenceat close approachof 138 000 km



Recent observations


Validation #1: reproducing Giotto results

We test our model byapplying it to 1P/Halley

Using a coma radius of200,000 km, we canreproduce the fluxGiotto recorded

103 104 1050.01

0.1

1

10

100

1000

r (km)

flu

x(m

−2

s−1)

Fulle et al. (2000) data, our model


http://adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000AJ....119.1968F&link_type=ABSTRACT


Recent observations


Validation #2: reproducing Stardust results

Stardust flew 300 kmfrom 81P/Wild 2

Coma radius was24,000 km at 1.7 au

We model impacts permass channel

1 10 100 1000

1

10

100

1000

M2

M1

m3 m2

m1

N (model)

N(m

easu

red

)

Tuzzolino et al. (2004) data, our model


http://adsabs.harvard.edu/abs/2004Sci...304.1776T


Recent observations


Validation #3: comparison with simulations4× 10−6g particles

−200 0 200

−200

0

200

x (103 km)

y(1

03km

)

−200 0 200

x (103 km)

0.001

0.01

0.1

1

Analytical model (left) and normalized simulations (right) inplane containing Mars (at origin), perpendicular to trajectory.

Simulations performed by Paul Wiegert, UWO.



Recent observations



−200 0 200

−200

0

200

x (103 km)

y(1

03km

)

−200 0 200

x (103 km)

0.001

0.01

0.1

1

Small scale simulations do not predict number of particles;fluence on right is multiplied by Ntheory/Nsim.

Simulations do illustrate (modest) deviance from sphericalmodel due to coma asymmetry and tail.



Recent observations



−200 0 200

−200

0

200

x (103 km)

y(1

03km

)

−200 0 200

x (103 km)

0.001

0.01

0.1

1

Simulated coma has large radius (200, 000 km) due to earlyassumed start of activity (10 AU)

Effective radius may be smaller – needs further study



Recent observations



−200 0 200

−200

0

200

x (103 km)

y(1

03km

)

−200 0 200

x (103 km)

0.001

0.01

0.1

1

Larger particles:

Have lower ejection velocityAre less subject to radiative forces



Recent observations


Validation #4: comparison with independent studies

Parallel effort to model comaparticle dynamics: Vaubaillonet al., 2014

Uses Af ρ rather thanmagnitude to scale dustproduction.

Results agree to within anorder of magnitude ... with thesame input parameters



Recent observations


Martian meteor shower

Meteor shower willaccompany Siding Spring

ZHR for 10−6 g particles∼ 30,000,000 at Mars

Subradiant nearOpportunity at dawn

MarsExpress may see up to1000 meteors per minute

10,704 km2 FOVm & 3 gNumbers fromAnastasios Margonis



Recent observations



1966 Leonids by A. Scott Murrell

Average flux of 100 micron orlarger meteoroids in low Earthorbit is 5× 10−6 m−2 per hour

Fluence due to Siding Springis 500 times higher(5 years of LEO exposure)

There has never been an eventlike this near Earth in recentmemory, with the possibleexception of the 1966 Leonids.


http://leonid.arc.nasa.gov/1966.html


Recent observations


Effects on the Martian atmosphere

Atmospheric effects

Energy deposition:

KE =

∫dσ

dmm dm × v2

2× πr2

M

1.14 megatons of TNT equivalent0.006% of solar irradiance: insignificant

Metal deposition probably more important(John Plane, Leeds)



Recent observations


Effects on the Martian system

Impact ejecta from the moons could last months or years(Apostolos Christou, Armagh)



Recent observations

Brightness monitoringObservational constraintsComparison with Hale-Bopp

Brightness monitoring

1 m at Siding Spring

Hubble

Multiple efforts to monitor Siding Spring:

NMSkies, 0.5m (MEO)

Siding Spring, 1m (MEO)

Siding Spring, 2m (Christou, Armagh)

NEOWISE

Hubble (PI: Jian-Yang Li)



Recent observations


Brightness monitoring

1234567

20◦

40◦

60◦

80◦

100◦

120◦

Heliocentric distance (au)

S-O

-Tan

gle

1234567

9

9.5

10


Ab

solu

tem

agn

itu

de

Asami et al., 2013

Cometas Obs

MEO



Recent observations


Syndyne calculations

– 25 –

Fig. 6.— Syndyne-synchrone computation for the master frames. North is up and east is

left.

Ye & Hui, 2014

Ye & Hui, 2014:

Shape of cometary tail isinfluenced by gravity andradiation pressure“Mostly large particles” basedon curvature of tailLow ejection velocity based oncompactness of the coma

Low ejection velocity= compact coma= much lower fluence at Mars



Recent observations


Hubble observations



Recent observations


Hubble observations

−20 0 20

−20

0

20

x (103 km)

y(1

03km

)

−20 0 20

x (103 km)

The coma does appear to be expanding slowly



Recent observations


Heliocentric magnitude: Hale-Bopp

Hale-Bopp had three phases of activity pre-perihelion (Kidger,1997)

∝ r−5 at large distances

∝ r−1 around 4 au (a “standstill”)

∝ r−3.5 at smaller heliocentric distances

Kidger notes that ice sublimation begins around 4 au



Recent observations


Heliocentric magnitude: Hale-Bopp

123456

−2

0

2

4

6


Hel

ioce

ntr

icm

agn

itu

de

Image credit: A. Kammerer



Recent observations


Heliocentric magnitude: Siding Spring

1234567

8.5

9

9.5

10

10.5


Ab

solu

tem

agn

itu

de

Asami et al., 2013

Cometas Obs

MEO



Recent observations

Summary

Comet C/2013 A1 (Siding Spring) will have close encounterwith Mars on October 19, 2014

Mars and spacecraft will pass through coma and tailcontaining meteoroids

Meteoroids (4.19× 10−6 g or larger): ∼ 1% chance of impactper square meter due to coma and tail

Continued monitoring is needed to better predict futurebehavior


The meteoroid fluence at Mars due to Comet C/2013 A1 ... McNaught 0.5 meter telescope Siding Spring,...

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