Mars Curiosity Rover

The Mars rover Curiosity is a huge leap forward from previous rover technology; this sophisticated device was created by NASA and was launched on the 26th November 2011. After its560-million-kilometer (350-million-mile) journey from Earth, the rover managed to perform some extremely complicated preprogrammed maneuvers in order to successfully land on Mars. This rover is an extremely expensive piece of technology, costing NASA some 2.5 billion dollars. This is the highest amount of money NASA has ever spent on a rover.

Curiosity’s landing in Gale Crater was called the 7 minutes of terror, because NASA would not know for 7 minutes if the landing was successful. (The signal takes 7 to 14 minutes to travel from Mars back to NASA.) NASA chose Gale Crater for a number of reasons, one of them being that it was a big and safe crater for landing.

The rover has a weight of approximately 900 kilograms (1,900 pounds).

The process of landing was as follows:

1.  Cruise stage: Curiosity approached the planet and made the final important calculations for a successful landing.
2. Cruise separation: Ten minutes before entering the Martian atmosphere, the cruise phase separated from the MSL and eventually burned up in the atmosphere.
3. Guided entry: Small rockets on the MSL craft fired to control its descent.
4. Peak heating: About eighty seconds after entering the atmosphere, the heat shield protected the MSL as it hit terminal velocity through the thickening Martian atmosphere. Temperatures reached 3,800 °F (2,100 °C).
5. Heat shield separation: Roughly 5 miles above the surface, the heat shield separated from the MSL.
6. Radar data collection: The MSL fired radar at the crater surface to determine the most suitable landing site in a predetermined zone.
7. Back shell separation: The back shell (with the parachute still attached) separated less than 2 kilometers (0.6 miles) from the surface.
8. The Sky crane lowered the rover using 3 thick metal wires.
9. Touchdown, which was obviously successful.

Overall, this rover is the most sophisticated piece of technology NASA has ever sent to Mars.

Why Is the Sky Blue?

We should begin with the Sun itself, a big hydrogen-fusing ball of plasma with a surface temperature of about 5,780 K (5,507°C or 9,944°F). At this temperature, the Sun radiates strongest in the green part of the spectrum. 

It is at this point that we can come to understand a little more about the light that the Sun is producing: It peaks in the green part of the spectrum, but a very broad range of electromagnetic radiation (light) is being given off. The Sun gives off light in a variety of forms, from X-rays and UV radiation (which causes sunburn), all the way through to radio waves. When the electromagnetic radiation eventually hits the Earth, just about the only part that doesn’t reach the surface is the X-rays, as they’re blocked by the atmosphere.

Now we’ve established that the Sun really is green, but this doesn’t really explain why the sky is blue. Or does it?

We started off at the Sun, and the next step along this little journey is the Earth’s atmosphere, where all the excitement happens.

When light enter the atmosphere, it has to pass through all the molecules it encounters. The more energetic part of the spectrum (blue) is scattered more than the less energetic (red), meaning that the less energetic light is able to pass through relatively unscathed. When the blue light is scattered it is scattered in all directions, causing the entire sky to be blue.

You might now be asking why the sky isn’t violet. We can see violet, so it is not at all unreasonable to ask this. The reason is actually somewhat related to the way that we see the Sun as being yellow as opposed to being green. Violet is the wavelength of light that is scattered the most because it is more energetic than the blue light. Our eyes, however, distinguish colour by “seeing” in three colours: red, green, and blue. This means that, to be able to see violet, we have to mix two colours together: red and blue. Since red light isn’t scattered much, there isn’t enough red for our eyes to process. This is why we don’t see the violet sky.