About Mars Globe

Mars Globe version 1.0

Introduction

The planet Mars has captured the imagination of humans since before recorded history began. To the ancients, it was a reddish point of light that slowly wandered through the night sky. The Romans named it Mars, after their god of war, but the planet has had many names in many cultures. (If you explore the terrain features in Mars Globe, you will discover some of them: many of the planet's dry river valleys are named after words for the planet in Earth's many languages.)

After Galileo Galilaei first used a telescope to observe the night sky in the early 1600s, it became clear that the planets are worlds, like our own - or unlike our own. But Mars is a small world, and at the very closest it gets to Earth, it is still at least 55 million kilometers (34 million miles) away. Galileo could only make out a bright disk. The very best view of Mars that can be obtained from Earth, using telescopes far superior to Galileo's, looks something like Mars Globe zoomed all the way out:

From Earth, a view even that good can only be obtained at intervals of approximately two years, when the orbits of Earth and Mars carry us relatively close together. At such times, the early observers of Mars stared through awkwardly-placed lenses for hours, night after night, waiting for Earth's turbulent atmosphere to hold still for a moment and grant a clear view of the Red Planet.

In the 1800s, observers such as Giovanni Schiaparelli could see that Mars had bright and dark areas, which turned with the planet as it rotated on its axis, once every 24.6 hours. Some of these features seemed to vary over time. The nature of these bright and dark areas was unknown. Were the dark areas seas? Or were they areas of vegetation, which grew darker or lighter with the seasons? Were the bright spots snow, or clouds? Schiaparelli also thought that he could see "canali," or channels, on Mars. Although this later turned out to be an optical illusion, the word, misinterpreted as "canals," touched off a firestorm of speculation which persisted for almost a hundred years. Did Mars have life, building the "canals"? Were there intelligent beings there, who might look up at a bluish point of light in the evening sky - the Earth - and ponder its nature?

The arrival of unmanned spacecraft in the 1960s and 70s, both in orbit and on the ground, began to answer these questions, and at first, the answers seemed bleak. Mars has no seas, and no areas of vegetation; the light and dark areas seen in history were, for the most part, areas of rock and dust. The atmosphere is very thin, and is quite unsuitable for life such as it exists on Earth. It is very cold on Mars; the temperature hardly ever rises above the freezing point of water at the surface. Much of that surface is covered with ancient craters, formed by the impact of meteors and asteroids over billions of years.

At first glance, Mars looked quite dead.

But then, we noticed more. Mars has many valleys which look like dry river valleys on Earth, and channels that look as if they were carved by massive floods of water in some earlier age. Although its atmosphere is very thin, it has clouds of water ice, which often cover large areas of the surface. Mars has a huge canyon named Valles Marineris, which is about the same length as the United States is from coast to coast. The planet has the largest volcanoes in the solar system, many times larger than volcanoes on earth, including the enormous Olympus Mons, "Mount Olympus." There is a vast low plain in the north, smooth and relatively devoid of craters, indicating that it is much younger geologically than the rugged southern highlands.

Clearly, Mars was once a more active world. How much water flowed there, and where did it go? Did the planet once have a thicker atmosphere? Billions of years ago, did it have lakes or even oceans on its surface? In short, was Mars once a world where life could have begun? Did life ever begin there? Could microscopic organisms still exist there even today, holding on to life in some ecological niche underground, or buried in ice, waiting for more clement times to return?

These latter questions are still mostly unanswered. But we know much more than we once did. Mars Globe, in addition to providing a view of the Red Planet as it appears from above, is intended to serve as an introduction to some of what we know about this mysterious world, and what we hope to learn in the future. A good place to start is with the Highlights, which provide a guided tour of some of Mars' most intriguing features. You can go to the Highlights menu and choose a starting point, then use the arrow buttons to zip from feature to feature, reading the descriptions as they appear. My thanks go to Emily Lakdawalla of The Planetary Society for editing the Highlight descriptions, adding some great information and making sure I didn't stray too far from current science.

But Mars Globe is really only a jumping-off point. In many of the descriptions of the terrain, I have included links to resources on the Internet, where you can find much more detailed information, images, and debate on the interpretation of Mars' features. The United States' National Aeronautics and Space Administration (NASA), the associated Jet Propulsion Laboratory (JPL), and the similar European Space Agency (ESA) do amazing work bringing images and information to the public, and I have included as many links to current NASA/JPL and ESA articles as I could manage. Wikipedia is a particularly valuable resource for historical information, and you will find many links to Wikipedia articles on those people who have contributed to the understanding or lore of Mars, and who now have Martian craters named in their honor. In the "People" menu you will find a rough chronology of these pioneers, so that you can explore the world from their perspective, as well.

Touch this link to begin your tour at Olympus Mons, the largest volcano in the solar system.

A Note on Realism

In this app an effort has been made to present a 'realistic' view of the planet Mars. However, in reality, Mars does not look the same from day to day. Clouds and sometimes dust storms come and go, covering large areas of the surface. The polar ice caps shrink or grow depending on the season. Frost coats Hellas Basin, then disappears. Over a period of years, even the global patterns of light and dark on the surface change significantly, as dust is transported by the wind. So it should be kept in mind that this globe represents an idealized "snapshot" of the planet circa mid-1999, when the majority of the Geodesy Campaign Mosaic was imaged by the orbiting Mars Global Surveyor spacecraft. Other representations of the planet, for example those based on the Viking Orbiter images taken in the late 1970s, look substantially different. But the terrain features of Mars remain, for the most part, the same; the exception being occasional new craters or gullies, which are all, at least so far, too small to be visible in this app. (The cause of the craters is well known; the cause of the gullies is one of the biggest mysteries on Mars today.)

To see what Mars looks like today, a good place to go is the MARCI Weather Report for the Week on the web.

It should also be noted that the original map used in this app is actually grayscale (black and white), and color was added by the program author, loosely based on actual data. It turns out that interpreting color data from spacecraft is a surprisingly difficult "dark art," and so my effort should be regarded as an approximation, or guess, of what Mars might look like to a human looking down from space.

Credits

The program is written by Michael Howard.

Special thanks to Emily Lakdawalla of The Planetary Society for editing the Highlight feature descriptions.

Coordinates and basic information for Martian terrain features are from the International Astronomical Union's Gazetteer of Planetary Nomenclature, published by the U.S. Geological Survey. Feature descriptions have been edited for readability, with additional content and links added by the program author.

The primary map of Mars used in this app is based on the Mars Orbiter Camera (MOC) Wide Angle Atlas. Credit: NASA/JPL/Malin Space Science Systems; colorized by Michael Howard.

Altimetry data is from the Mars Orbiter Laser Altimeter (MOLA) instrument; credit: NASA/MOLA Science Team.

Mars time is computed using the algorithm documented on the Mars 24 website: http://www.giss.nasa.gov/tools/mars24/. We recommend the Mars24 desktop application for all your Mars timekeeping needs.

Thanks to the admins and moderators at unmannedspaceflight.com who reviewed beta versions of this app and suggested improvements, especially Doug Ellison (who hosts the forum), Joe Mansfield, James Canvin, and Daniel Crotty.

Mars Globe version 1.0

Introduction

A Note on Realism

Further Reading

Credits