ABSTRACT
Neither manned landings nor stationary or slow, short range robotic probes such as Mars Pathfinder can explore the surface area of Mars, 144 million square kilometers comprising as much surface as all the continents and islands on Earth. For example, a half million manned or robotic landings capable of surveying a 300 square kilometer region of the Martian surface will be needed to survey the surface of Mars once. The handful of astronauts likely to be sent to Mars in manned missions, even equipped with rocket planes or ballistic hoppers, will directly survey only a tiny fraction of the planet. A complete survey of Mars will require high-speed low altitude or ground based devices, either remotely piloted, semi-autonomous, or autonomous, such as airplanes, balloons, or high-speed rovers. Fast moving robotic explorers will need high frame rate imaging, such as digital video, to properly survey the planet and for remote operation either by astronauts on Mars or mission control on Earth. They will also generate very high data rates compared to current Mars to Earth communication data rates.
This paper reviews concepts for unmanned aerial
exploration of Mars including airplanes, balloons and more exotic
vehicles. The primary focus of the article is on Mars airplanes. A
brief history of aerial Mars exploration concepts is presented. The
major scientific, engineering, and operational objectives - why do it
-- of unmanned aerial missions on Mars are discussed. Some discussion
of objectives appropriate for privately funded aerial missions on Mars
is presented. Major engineering issues for aerial vehicles on Mars are
discussed including some discussion of the engineering and economics of
manufacturing fleets of aerial vehicles for Mars exploration.
Lindenmayer systems or L-systems are a mathematical model of plant growth and cell differentiation proposed by the late biologist Aristid Lindenmayer. L-systems can generate photorealistic computer graphics models of trees, flowers, and other plants as well as other complex structures. An L-system is a set of rewriting rules such as A ==> Aa and A ==> a that replace the left hand side of the rule with the right hand side. The rewriting rules are applied repeatedly until only the terminal symbols, such as (a) in the example, that only appear on the right hand sides of the rules remain.
A nanometer scale L-system is a set of simple nanomachines that replace target modules with a payload of replacement modules. At nanometer scales, the nanomachines may be able to use thermal diffusion for transport and complementary shapes and chemical affinities, molecular recognition, for targeting. Internal power sources, propulsion systems, guidance, navigation, and control systems may not be needed. Each nanomachine in a nanometer scale L-system is only a few nanometers in cross-section and probably much easier to fabricate than a complex nanorobot. Their small size may enable them to non-destructively enter fragile structure such as cells. Nanometer scale L-systems may be able to assemble complex structures and complex systems of interacting components. The theory of nanometer scale L-systems is presented as well as a discussion of experimental tests and potential practical applications such as the programmed repair of chromosomal and genetic damage in cancer cells.
NASA Ames Research Center
Moffett Field, CA
April 7-11, 2002
Press Release
Poster (HTML)
Abstract from Book of Abstracts
Updated Version of Paper Presented at the Instruments, Methods, and Missions for Astrobiology IV Conference
On to Mars is distributed by Univelt Inc. (http://www.univelt.com/)
ABSTRACT
Neither manned landings nor short-range robotic probes such as Mars Pathfinder can explore more than a small fraction of the surface of Mars, 144 million square kilometers comprising as much surface area as all the continents and islands on Earth. Complete exploration of Mars to find or conclusively rule out important discoveries such a past or present life will require high speed low-altitude or ground-based probes such as airplanes, balloons, or high-speed rovers. These devices will need high frame-rate imaging such as digital video to explore the planet and for remote operation either by astronauts on Mars or mission control on Earth. A major limitation for transmission of video both on Mars and especially between Mars and Earth is the limited bandwidths available, currently less than 100 Kilobits/seconds between Mars and Earth when line of sight is available. One solution is to establish a network of communications satellites in Mars orbit. Even with a communications network, bandwidth will be limited, especially between Mars and Earth. A complementary approach is to develop very low bitrate video compression algorithms, e.g. VHS videotape quality at 56 Kilobits/second. Methods that may be able to achieve this such as the H.26L and MPEG-4 video coding standards, contour-based image coding, and object-based image coding are discussed, including applications and special issues on Mars and in deep space such as the high bit error rates of deep space communication links.
Note: This was written and presented in 2002, before the breakthrough in low bitrate video coding that reached the market in 2003.
Press Release
ABSTRACT
It is suggested that life originated in a three-step process referred to as the jigsaw model. RNA, proteins, or similar organic molecules polymerized in a dehydrated carbon-rich environment, on surfaces in a carbon-rich environment, or in another environment where polymerization occurs. These polymers subsequently entered an aqueous environment where they folded into compact structures. It is argued that the folding of randomly generated polymers such as RNA or proteins in water tends to partition the folded polymer into domains with hydrophobic cores and matching shapes to minimize energy. In the aqueous environment, hydrolysis or other reactions fragmented the compact structures into two or more matching molecules, occasionally producing simple living systems, also known as autocatalytic sets of molecules. It is argued that the hydrolysis of folded polymers such as RNA or proteins is not random. The hydrophobic cores of the domains are rarely bisected due to the energy requirements in water. Hydrolysis preferentially fragments the folded polymers into pieces with complementary structures and chemical affinities. Thus the probability of producing a system of matched, interacting molecules in prebiotic chemistry is much higher than usually estimated. Environments where this process may occur are identified. For example, the jigsaw model suggests life may have originated at a seep of carbonaceous fluids beneath the ocean. The polymerization occurred beneath the sea floor. The folding and fragmentation occurred in the ocean. The implications of this hypothesis for seeking life or prebiotic chemistry in the Solar System are explored.
