Mars Bow Shock

24 Aug 2017

At ... solar EUV (ultra violet radiation) is an important feature of the solar wind. As energetic particles of the solar wind cross space inside the solar system they are modified by cosmic objects in their path - including the planets. This pieces is also derived from PhysOrg we may note but the comments are interesting. Scientists already are aware of the bow shock, upstream of planets - like the bow of a ship (the waves that rises up at the side and behind). In the case of a ship's bow shock the water is slowed - and the same thing happens with the solar wind. Mars is such an object - with a bow shock. The obstacle on Mars is its ionosphere - a region of electrically charged particles in the upper atmosphere. Of  course, the atmosphere of Mars is thin - but an ionosphere is still relevant. Variations in the ionosphere and the exosphere play a role in the location of the bow shock boundary. They cause a slow down in the solar wind and shift the position of the bow shock.

Also, variations in bow shock distances also correlates with annual changes in the onset of dust in the Martian atmosphere. The dust storm season begins when Mars it at perihelion - when the planet is warmer and closest to the Sun, and receives greater solar radiation.

Voyager 400 Years On.

At ... it is 40 years since NASA launched the Voyager space probes, and CSIRO operates the tracking station at Canberra in Australia. The major purpose of the Voyager missions was to fly to Jupiter and Saturn. It was then hoped they would go on to visit (one of them) Neptune and Uranus, taking advantage of an alignment of planets that will not recurr for another 175 years.

Both Voyagers have long since left the outer planets behind - following different directions (but still sending data back to the Earth). It will be 40,000 years before Voyager 2 passes the closes solar system and 296,000 years before Voyager 1 passes the star Sirius.