The applet was implemented using 2-body methods, and hence should not be used for determining accurate long-term trajectories (over several years or decades) or planetary encounter circumstance

Simulation of the close approach of C/2013 A1 to Mars in Celestia using the latest MPC elements (click to embiggen)

Simulation of the telescopic view of Mars and C/2012 A1 on October 19 as seen from Adelaide near closest approach..

Image of the JPL Orbit widget which shows Mars and comet C/2013 A1 on top of each other on October 19, 2014, but note the caveat in the applet that says " A reader pointed out that the JPL Orbit Diagram for comet C/2013 A1 (Siding Spring) shows the Comet and Mars on top of each other on October 19, 2014 (see the diagram here ). Does this indicate an impact between the comet and Mars?No, if you go to the bottom of the orbit diagram and click on the [show close approach] link, you will see that the nominal close approach is 0.006 AU (compare this to the 0.00023 AU close approach of 2012 DA14 , which misses us by two Earth diameters).The error associated with this estimate includes an impact though (and a maximum miss of 0.24 AU), so an impact can't be ruled out at this stage.However, as further observations are added and the orbit is refined, we will have a better idea of whether it will impact. The latest Minor Planet Ephemeris data suggests that an impact is unlikely, with a nominal pass of 0.015 AU (2,277,700 Km from Mars's surface).Importing the latest elements into SkyMap or Stellarium suggests that from Earth we will see the comet and Mars less than 2 minutes of arc from each other, which will look quite nice in telescope eye pieces (but hard to image as the comet will be a dim magnitude 8.5 and Mars bright).I've also made a Celestia file for you. As usual, copy the code below and save as it as a text file 2013A1.ssc in the Celestia extras folder.======================2013A1.ssc============================="Siding-Spring:C2013 A1" "Sol"#Close approach of this comet to MarsClass "comet" # Just copying the data for HalleyMesh "halley.cmod"Texture "asteroid.jpg"Radius 3 # best guess at maximum semi-axisMeshCenter [ -0.338 1.303 0.230 ]EllipticalOrbitEpoch 2456955.47179 # 2014 25 OctPeriod 217204.51919319 # (q/(1-e))^1.5 hyperbolic orbitSemiMajorAxis -3613.3711384783 #Hyperbolic orbitPericenterDistance 1.396000248531628Eccentricity 1.000467Inclination 128.9984AscendingNode 300.9204ArgOfPericenter 2.4695#MeanAnomaly 359.9970184682824 #MA messes up hyperbolic orbits# Again, this data is copied straight from the ssc files for Halleys’ Comet# chaotic rotation, imperfectly defined:# this version from "The New Solar System", 4th Edition; Eds.# JK Beatty, CC Petersen, A ChaikinPrecessingRotationPeriod 170 # 7.1 day axial rotation periodInclination 66PrecessionPeriod 3457004.12 # 3.7 day precession periodAlbedo 0.8===========================================================

Labels: celestia, comet, comets, Mars