This paper explores a simple question: How would we provide a high-quality search experience on Mars, where the fundamental physical limit is speed-of-light propagation delays on the order of tens of minutes? On Earth, users are accustomed to nearly instantaneous response times from search engines. Is it possible to overcome orders-of-magnitude longer latency to provide a tolerable user experience on Mars? In this paper, we formulate the searching from Mars problem as a tradeoff between "effort" (waiting for responses from Earth) and "data transfer" (pre-fetching or caching data on Mars). The contribution of our work is articulating this design space and presenting two case studies that explore the effectiveness of baseline techniques, using publicly available data from the TREC Total Recall and Sessions Tracks. We intend for this research problem to be aspirational and inspirational - even if one is not convinced by the premise of Mars colonization, there are Earth-based scenarios such as searching from a rural village in India that share similar constraints, thus making the problem worthy of exploration and attention from researchers.
In this work, we assume that a functional interplanetary Internet already exists, and that the only problem we need to overcome is latency at the application layer. This is not an unrealistic assumption as other researchers have been exploring high-latency network links in the context of what is known as delay-tolerant networking (see, for example, IETF RFC 4838 https: tools.ietf.org html rfc4838 ) and NASA has already begun experimental deployments on the International Space Station. http: www.nasa.gov mission_pages station research experiments 730.html Once again, there are many similarities between building interplanetary connectivity and enhancing connectivity in developing regions. Examples of the latter include DakNet @cite_0 , deploying wifi access points on buses to provide intermittent connectivity to users along their routes and the work of @cite_15 to ferry data using mechanical backhaul (i.e., sneakernet)---which isn't very different from our proposal to put a cache of the web on a Mars-bound rocket (more details later).
@cite_0 @cite_15
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DakNet provides extraordinarily low-cost digital communication, letting remote villages leapfrog past the expense of traditional connectivity solutions and begin development of a full-coverage broadband wireless infrastructure. What is the basis for a progressive, market-driven migration from e-governance to universal broadband connectivity that local users will pay for? DakNet, an ad hoc network that uses wireless technology to provide asynchronous digital connectivity, is evidence that the marriage of wireless and asynchronous service may indeed be the beginning of a road to universal broadband connectivity. DakNet has been successfully deployed in remote parts of both India and Cambodia at a cost two orders of magnitude less than that of traditional landline solutions. Rural kiosks in developing countries provide a variety of services such as birth, marriage, and death certificates, electricity bill collection, land records, email services, and consulting on medical and agricultural problems. Fundamental to a kiosk's operation is its connection to the Internet. Network connectivity today is primarily provided by dialup telephone, although Very Small Aperture Terminals (VSAT) or long-distance wireless links are also being deployed. These solutions tend to be both expensive and failure prone. Instead, we propose the use of buses and cars as "mechanical backhaul" devices to carry data to and from a village and an internet gateway. Building on the pioneering lead of Daknet [15], and extending the Delay Tolerant Networking Research Group architecture [24], we describe a comprehensive solution, encompassing naming, addressing, forwarding, routing, identity management, application support, and security. We believe that this architecture not only meets the top-level goals of low cost and robustness, but also exposes fundamental architectural principles necessary for any such design. We also describe our experiences in implementing a prototype of this architecture.