The first permanent settlement on Mars will be of a size that does not necessarily require a distributed computer network. Nevertheless, there is the need for a mutual communication between people on Mars and people on Earth. The Martian settlement can, therefore, be connected to the terrestrial Internet, which in fact makes it an Interplanetary Internet.
The speed of any communication between Mars and Earth is limited to the speed of light, which results in a minimum delay (when the planets are closest to each other) of about 8 minutes for one way. This delay increases to approximately 18 minutes when the planets are in conjunction. This causes another issue as the Sun will be blocking the Line Of Sight (LOS) between the planets, communication signals will need to be re-routed via an interplanetary network, increasing the time taken for signals to travel between Earth and Mars. Without special buffering the result of a mouse click appears 16 minutes (minimum), or over 36 minutes (maximum), later on the screen. Time for HTML download will add to this lag. So, at worst, a complete terrestrial web page may take over 40 minutes to display on a Mars-based computer.
Concept for a Martian Internet
The first step can be a single computer and a radio transmitter brought from Earth to Mars. On Earth there is a corresponding radio transmitter, or network of global transmitters, and a buffered interface to Earth's Internet. Internet access may only be available during certain time frames (depending on Earth/Mars phase and availability of communication satellites).
An extension is possible to widen the time windows with additional transmitters on other continents and relay stations orbiting Earth and Mars.
The buffer on Earth side should have some additional functionality:
- Collect all files (e.g. pictures) that are related to a requested HTML page and send them together with the HTML page. This reduces the time from mouse click to complete screen display of up to 40 minutes.
- Reduce resolution of pictures if appropriate.
- Compress data stream.
- Add redundancy to the signal to allow data reconstruction for lost bits. The re-transmission of TCP data packets is awfully time consuming in this case and should be avoided.
- Another method is to construct a new method of HTML transmission (similar to the cut-down WAP service for cell phones and other mobile devices). Images and graphics may be stripped from websites leaving only HTML text.
Solutions to the Internet communications "lag"
The first Mars base
In the first instance (when the first colony is being constructed) it may not be possible to have a functioning "Internet" as we currently understand it. Colonists should, however, have email contact for personal and science-based contact with Earth.
An established Mars settlement
In time, the technological capabilities of a Mars settlement will increase. Also, technological advances on Earth will have accelerated, so an established Mars colony may receive new technologies as it becomes available on Earth.
Assuming an established Mars settlement will consist of several buildings, or separate settlement sites spaced several kilometers apart, computer communications will be very important. The establishment of a basic "Mars Internet" would therefore be desirable to improve communications around the planet. A Mars Internet (or Marsnet) could be routed via satellites in Mars orbit, use long distance Internet protocols and cell towers or lines may be laid across the Mars surface directly. Using technology developed on Earth, Marsnet would develop quickly, and depending on the number of colonists, the first Mars websites may be created rapidly.
However advanced a Marsnet becomes, communications with the terrestrial Internet will still be limited by the speed of light. The time lag for Earth to Mars two way communications varies from 8 to 40 minutes. There is only one solutions to this problem: Cache (store) some of the terrestrial Internet contents on Mars-based servers, with regularly uploading new information or on demand. The current number of websites on the Internet totals over 100 million (as of Feb. 2007). By the time a Mars colony is established, this number will have exponentially increased. So, only a subset can be cached. The selected contents may comprise "mission critical" sites such as NASA's or ESA's web pages, Wikipedia, some online news magazines, scientific and technical sites, artwork, etc.
When Mars is in opposition, the sun creates an obstacle to communications with Earth. Relay satellites may be required.
First use cases
- Technology information from Earth to Mars
- Scientific results from Mars to Earth
- Personal E-Mails in both directions
Eventually the number of internet servers and web homepages located in Mars will increase, thus solving many of the problems with the use of Earth based homepages.
The present communication rates of Martian orbiters is 2 MBps down to Mars and 2 MBps towards Earth. Mars reconnaissance orbiter does have the capacity to reach 6 MBps, with as little as 35 Watts of power. Modern telecom Satellites such as Viasat-2 have a power of about 18 kW and could provide many orders of magnitude of supplementary bandwidth.
Communication rates may be quite high. For 1000 people, a rate of 20 GBps might be a good number. A Viasat-2 analog could possibly provide up to 300 GBps.