In our previous article, we started with an introduction to the Messenger space probe heading for mercury. Today we will discuss about further details such as its journey and discoveries.
Traveling to Mercury requires an extremely large velocity change (delta-v) because Mercury’s orbit is deep in the Sun’s gravity well. On a direct course from Earth to Mercury, a spacecraft is constantly accelerated as it falls toward the Sun and will arrive at Mercury with a velocity too high to achieve orbit without excessive use of fuel.
For planets with an atmosphere, such as Venus and Mars, spacecraft can minimize their fuel consumption upon arrival by using friction with the atmosphere to enter orbit (aerocapture), or can briefly fire their rocket engines to enter into orbit followed by a reduction of the orbit by aerobraking. However, the tenuous atmosphere of Mercury is far too thin for these maneuvers.
Instead, MESSENGER extensively used gravity assist maneuvers at Earth, Venus, and Mercury to reduce the speed relative to Mercury, then used its large rocket engine to enter into an elliptical orbit around the planet. The multi-flyby process greatly reduced the amount of propellant necessary to slow the spacecraft, but at the cost of prolonging the trip by many years and to a total distance of 7.9 billion kilometers (4.9 billion miles).
The elongated orbit had two other benefits: It allowed the spacecraft time to cool after the times it was between the hot surface of Mercury and the Sun, and also it allowed the spacecraft to measure the effects of solar wind and the magnetic fields of the planet at various distances while still allowing close-up measurements and photographs of the surface and exosphere.
The spacecraft completed its primary yearlong mission on March 17, 2012, having taken nearly 100,000 images of the surface of Mercury.
Among its initial discoveries was finding high concentrations of magnesium and calcium on Mercury’s night side, identifying a significant northward offset of Mercury’s magnetic field from the planet’s center, finding large amounts of water in Mercury’s exosphere, and revealing evidence of past volcanic activity on the surface.
During its first extended mission, the spacecraft found evidence of water ice at Mercury’s poles, frozen at locations that never see the sunlight (made possible by the fact that the tilt of Mercury’s rotational axis is almost zero.)
Here is the summary of the key events of the Messenger space probe.
With this, we complete an overview of the Messenger space probe. In our next article, we will be coming up with an exciting topic, which all space enthusiasts are interested in. Any guesses?
- Image Credits: NASA