This is an update on Comet C/2013 A1 Siding Spring from my last post on 6-30. Nasa is now saying there is a minimum risk. I say look at the pic below and decide how potentially dangerous this comet is for yourself. It’s a very close flyby…JP
As Comet C/2013 A1 Siding Spring heads toward a close flyby of Mars on October 19, 2014, NASA and ESA are both taking steps to protect their Mars orbiters, while still preserving opportunities to gather valuable scientific data. Six days after passing Mars, the comet will reach its closest approach to the Sun (perihelion) at about 209 million km (130 million miles).
It will be the second comet to visit Mars in 12 months, following Comet ISON in October 2013. ISON passed some 10 000 000 km from the planet, but Siding Spring will flyby much closer. Current estimates put Siding Spring’s miss distance at just about 132 000 km (82 000 miles) from the surface.
The comet’s nucleus will be shedding material hurtling at about 56 kilometers (35 miles) per second, relative to Mars and Mars-orbiting spacecraft. At that velocity, even the smallest particle – estimated to be about half a millimeter (one-fiftieth of an inch) across – could cause significant damage to a spacecraft.
NASA currently operates two Mars orbiters, with a third on its way and expected to arrive in Martian orbit just a month before the comet flyby. ESA has one spacecraft there, Mars Express. India’s Mars Orbiter Mission launched late 2013 is also on the way and will arrive about three weeks before Siding Spring.
Teams operating the orbiters plan to have spacecraft positioned on the opposite side of the Red Planet when the comet is most likely to pass by.
The hazard is not an impact of the comet nucleus, but the trail of debris coming from it. Using constraints provided by Earth-based observations, the modeling results indicate that the hazard is not as great as first anticipated. Mars will be right at the edge of the debris cloud, so it might encounter some of the particles — or it might not. – Rich Zurek, chief scientist for the Mars Exploration Program at NASA’s Jet Propulsion Laboratory in Pasadena, California.
During the day’s events, the smallest distance between Siding Spring’s nucleus and Mars will be less than one-tenth the distance of any known previous Earthly comet flyby. The period of greatest risk to orbiting spacecraft will start about 90 minutes later and last about 20 minutes, when Mars will come closest to the center of the widening dust trail from the nucleus.
NASA’s Mars Reconnaissance Orbiter (MRO) made one orbit-adjustment maneuver on July 2 as part of the process of repositioning the spacecraft for the October 19th event. An additional maneuver is planned for August 27. The team operating NASA’s Mars Odyssey orbiter is planning a similar maneuver on August 5 to put that spacecraft on track to be in the right place at the right time, as well.
NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft is on its way to the Red Planet and will enter orbit on September 21. The MAVEN team is planning to conduct a precautionary maneuver on October 9, prior to the start of the mission’s main science phase in early November.
Siding Spring by the numbers
Date of comet closest approach (CA): 19 October 19, 2014
Time of CA: ~18:28 UTC
*Estimated distance of comet from Mars at CA: 136 000 km from center | 132 000 km from surface
Comet nucleus diameter: Unknown
Coma radius: Likely to engulf Mars
Time for Mars to pass through coma: Several hours (ESA’s Mars Express now orbits Mars every 7 hours)
Velocity of cometary dust particles: 56 km/second
Dust particles produced by comet (as of 28/1/14): 100 kg/second
Sources: ESA, NASA/JPL-Caltech
Source The Watchers