The easiest way to send a spacecraft to Mars is to fling it into space at just the right angle. If done right, the probe will hurtle along a crazy-looking elliptical route for about nine months until it reaches the red planet's field of gravity and begins circling its target.
The best time to launch such a mission is once every 26 months, when the distance between Earth and Mars shortens to a mere 60 million kilometers -- the nearest the celestial neighbors get to one another. Astronomers call this period "close approach," and the next one will occur on Oct. 6.
