Lonniee Reschly, age 10, of Washington, Ia., for his question:

How far is Mars from the sun?

Mars is one of our next door neighbor planets. Its orbit is outside the Earth's orbit, and so it is always farther from the sun than we are. In January, the Earth is 3 million miles closer to the sun than it is in July? The distance between Mars and the sun varies by more than 26 million miles. Thee average distance between Mars and thee sun is about 141 million miles. But This figure does not give us an accurate day by day picture of the distance between Mars and the sun. Sometimes the little red plant is 155 million miles from the sun, and sometimes it swings closer to the sun than 129 million miles. The Martian year is Equal to 687 Earth days. This is the time it takes our neighboring planet to swing once around its orbit. We can add up the daily distance Between Mars and the sun and divide the high numlber by 687. This g1ves 11S the average Distance between Mars and the sun. This figure would be accurate if Mars were Always the sable distance from the sun. But this is not so. Mars may be 13 million Miles closer to or farther from the sun than this average distance. This happens because the orbit of Mars is not a circle  far from it. It is an Oval shaped path ca11ed an ellipse. The sun is not at the center of the Martian Orbit, which is why Mars is sometimes nearer and sometimes farther from the sun.

The Shortesrt dlstance between the sun and the planet's orbit is ca11ed the perihelion. The longest distance between the planet's orbit and the sun is called the aphelion. In the Martian year of 687 days, the little plant travels from perihelion to  Aphelion and back to perihelion. At perihelion, it is 128.75 million mils from the Sun. At aphelion, it is 155 million mils from the sun. For the rest of the Martian  Year, the distance between Mars and the sun is somewhere between these two opposite If the orbit of Mars were a circle, the distance between the planet and the sun would always be the same. Then the average distance would be correct. Mars would be  141 million miles from the sun Every day of the Martian year. But the orbit is an  e11ipse, and the distance between Mars and the sun varies by more than 26 million miles.  The Earth's orbit is not a true circle either. But it is not such an oval shaped erllipse as the orbit of Mars. The earth is at perihelion in Early January. Then it is only about 91.5 million miles from the sun. In July, it is at aphelion and about 94.5 million miles from the sun. The average distance is almost 93 million miles.