What’s Out Tonight?

A general ASTRONOMY site to get you started exploring the night sky


Facts about Mars 

• Fourth planet from the Sun 
• It’s a Terrestial Planet & may have microbial life in its soil

Diameter: 4,228 miles (about 1/2 Earth’s) 
Mass: 0.12 of Earth’s mass 
Density: 3.95 where water = 1 (Earth is 5.5) 
Gravity: 1/3 of Earth’s 
Albedo (% of Sunlight reflected): 15% 
Rotation on Axis: 24 hours, 37 minutes 
Tilt on Axis: 25.3° degrees compared to Earth’s 23.4°

Distance from Sun: 141,640,000 miles 
Revolution about Sun: 1.9 years or 687 days 
Inclination of Orbit to Earth’s Orbit: 1.85° 

Atmosphere: 95% Carbon Dioxide, 2.7% Nitrogen, 1.6% Argon, 0.2% Oxygen (Earth has 77% Nitrogen and 21% Oxygen 
Temperature: Ranges from –207° F to +80° F. The high is just about the surface, at noon and at the equator during summer. 

Moons: 2 irregularily shaped moons, Phobes (17x13 miles) and Deimos (10x8 miles) 

Most interesting features in a small telescope: Even when Mars is at its closest, it is relatively small, but with some patience and repeated observations over a few weeks, you will be able to see polar caps, clouds and the darker-colored surface areas. And different features can be seen as the planet rotates. When the north pole is facing Earth, it is very easy to see this white cap.

Picture from the first lander on Mars, Viking, in 1976. Dr. Alan Binder, a good friend of mine was one of a few people in charge of the imaging.

The Planet Mars

We identify with Mars more than any other Planet because Mars might have had or still may harbor microbal life. In the first half of this century, the United States and other countries will deluge Mars with numerous exploratory vehicles and possibly a manned mission to answer this question. Additionally, Mars is the second most hospitable Planet in the Solar System — the only Planet that humankind might be able to colonize. It has an abundance of frozen water at its North Pole, a major element needed to sustain a colony. 

What happened to the canals? 
Mars never had any canals! During the late 1800s and early 1900s, several astronomers thought they saw a network of lines interlacing the surface of Mars, which became known as “canals.” Maps of the canals were even drawn and published. However, no evidence was ever found for them. They are believed to be honest mistakes—the result of active imaginations. None of the exploratory spacecraft sent to Mars have found anything that could even be misconstrued as canals. 

Major features on Mars 
Mars has several unique features with the most notable shown in pictures to the right. Of special note to the observer are its poles, surface coloration and clouds. The light and dark surface colorations are caused by a color difference between sand and rock. 

Identifying Mars 
Mars is easy to find in the sky near opposition (this is when it is closest to the Earth and it is also the time when Mars is rising in the east as the Sun is setting in the west) because it is bright and “red” in color, shining steadily around magnitude –2. When Mars is not at opposition, its magnitude and conspicuousness fade to +2, making it easy to miss. 

Observing Mars 
Mars is small, so it is best observed around opposition when it is closest to the Earth and appears its largest. Oppositions with Mars occur about every 26 months, however, some oppositions bring us much closer to Mars than others because of the elliptical shape of orbits. The distance between Earth and Mars at opposition can vary from 35,000,000 to 63,000,000 miles. This difference effectively doubles the size of Mars in a telescope. Unfortunately, the next opposition that makes Mars a reasonable size does not occur until 2018. Although the polar caps and surface coloration can be seen in small telescopes (4-inch to 6-inch), they can be subtle, especially the surface coloration. For this reason, Mars is often disappointing to first-time observers who just take a glimpse at the planet. So, here are some suggestion to help maximize your viewing of Mars’ surface features. 

1. Try to observe Mars often from one month before to one month after opposition. Repetitive viewing will increase your familiarity with this Planet and increase your chance of observing on a good night. Additionally, you will be able to see the different sides and all of the surface markings on Mars if you observe over a period of time. 

2. Use a minimum magnification of 100x, but 200x to 300x is preferable. Achieving higher magnifications is dependent on your telescope and atmospheric conditions. 

3. Observe Mars when it is highest in the sky in order to minimize atmospheric disturbance. This will occur around midnight during opposition. It is more difficult to see the surface markings when Mars is low in the sky. The worst part about observing later is staying up or waking up. But, it is worth it. Mars is only at opposition every couple of years. 

4. When you are looking at Mars through a telescope, you will notice that there are split-second moments when the view of the surface appears clear. It is during these moments of clarity that the best glimpses will occur. It is a rare night when you can look directly at Mars and plainly see the subtleties of the surface markings for an extended period of time. 

5. Several months preceding opposition, the popular monthly astronomy magazines usually carry in-depth articles which should prove helpful. Often, they include current maps of the surface markings and charts to calculate the side of Mars that will be facing toward Earth when you observe. 

6. If you follow the suggestions above and still cannot see surface markings, here are some possible reasons why. a) Wind storms on Mars could be kicking up dust and obliterating the surface markings. Search the internet to check on Mars’ weather. b) Your telescope optics may not be properly aligned. Ask an astronomy club member or a telescope store to check out your telescope. c) The turbulence in Earth’s atmosphere may be affecting telescope image quality, so keep trying. d) Finally, remember that if you take your telescope from the warm interior of your home to the cold outside, it will take up to an hour for the telescope optics to cool and settle down. The image of Mars during this time will be blurry. Keep your telescope outside or in an unheated space before observing.

Moon of Mars.  Phobos, left, is 17x13 miles in size and orbits Mars every 7.7 hours at a distance of 5,380 miles. Deimos, right, is 10x8 miles in size and orbits Mars every 1.3 days at a distance of 14,580 miles.

The surface coloration on Mars can be seen in small telescopes and it is one of the features amateurs enjoy viewing. The large dark appendage is Syrtis Major. The large white area below it is not the south pole but clouds over Hellas (see below).

The giant impact basin known as Hellas is the lowest elevation on the planet (deep blue oval). It is often shrouded in clouds and can thus be confused with the south pole.You can see the clouds over Hellas at the bottom of the above picture.

Olympus Mons, the largest inactive volcano in the solar system. This is a “shield” volcano and the total area of the lava flow is the same area as the state of Arizona. The central cauldron is about 55 miles across at its widest part. Sometimes clouds hover over the Volcano—clouds that are possible to see in small telescopes.

The North Polar Cap on Mars is very distinct and easy to see in small telescopes, however, it needs to be facing Earth to see it. Yes, sometimes Mars’ North pole is angled and facing away from our line of sight. When it is visible, it is a very bright white cap on top of the planet.

Mars is about 1/2 the diameter of Earth. Its surface area is about the same as Earth’s total land masses. Although Mars is “small,” it has an incredibly long “Grand Canyon” called Valles ​Marineris that is longer than the United States and reaches 4 miles deep. Our Grand Canyon is 227 miles long and 1.1 miles deep. Valles ​Marineris is not conspicious in any small telescope—see E in the photo below for its location. 

Major Surface Features on Mars

A. Clouds atop Mars’ highest point and largest volcano, Olympus Mons 
B. Arcadia Plain 
C. Chain of three large volcanos 
D. Tharsis Plain 
E. Valles Marineris chasm 
F. Solis Lacus 
G. Mare Acidalium 
H. Landing site of Viking 1, 1976 
I. Landing site of Pathfinder, 1997 
J. Chryse 
K. Mare Erythraeum 
L. North Pole of Mars 
M. Plain of Arabia 
N. Sinus Sabaeus 

O. Utopia 
P. Syrtis Major (some report this as being bluish in color) 
Q. Iapygia 
R. Hellas, a giant impact crater that is covered with clouds (in this picture and most of the time). This is Mars’ lowest elevation. 
S. Alcyonius Nodus 
T. Mare Tyrrhenum 
U. Landing site of Viking 2, 1976 
V. Stymphalius Lacus 
W. Mare Cimmerium 
X. Memmonia Plain 

Two Notes: In the above picture, the South Pole is shrouded in polar clouds. Names of features vary slightly among reference sources.

Direction of rotation >>