SOHO/LASCO view of a coronal mass ejection in 2004
This animation shows a series of images that depict the solar corona, the hot outer atmosphere of the Sun, which consists of turbulent plasma at temperatures of millions of degrees.
The images are from the C3 camera of the Large Angle and Spectrometric Coronagraph (LASCO) on board the ESA/NASA SOHO mission. The Sun itself is blocked out in the images, with the size of the Sun's disc indicated by the central white circle. The position of Mars on the plane of the sky is indicated at the beginning of the animation.
These images were recorded on 3 September 2004, from 9:42 to 20:42 UT. During this time interval, a Coronal Mass Ejection (CME) occurred. CMEs are gigantic eruptions that release enormous amounts of matter and energy from the Sun through the corona and into space. The onset of the CME can be seen in the image taken at 11:18 UT, and its propagation away from the Sun can be followed in the subsequent images. In the interval between the images taken at 14:18 and 14:42, the shock front of the CME first crossed the line of sight to Mars, and additional material from the CME continued doing so for several hours.
On the same date, radio-sounding measurements of the solar corona were performed with ESA's Mars Express spacecraft, exploiting the fact that Mars was located almost behind the Sun on a line of sight from Earth. On their way to our planet, radio signals sent out by the spacecraft travelled through the Sun's corona and the disturbance caused to them by the CME could be clearly identified in the signal received on Earth.