Was ist Leben

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Biochemie und Exobiologie

Einleitung
und letztlich in höchst rätselhaften Fähigkeit der Materie zur Selbstorganisation begründet.

Leben auf der Basis von Kohlenstoff

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Kohlenstoff das Element, das die am höchsten ausgeprägte Fähigkeit besitzt, sich mit sich selbst zu verbinden. Kohlenstoff baut Moleküle in Form von Ketten (z.B. Butan C4H10 oder Oktan C8H20), Ringen (z.B. Benzol C6H12), Mehrfachringen (z.B. Kokain), spiralförmigen (z.B. RNS Ribonukleinsäure) und kugelförmigen (z.B. Fullerene) Körpern auf.

Wasser H2O, Polarität des Wassers, Häufigkeit der Elemente H und O und Ammoniak NH3


Abb. 1: Ketten: Oktan-Molekül


Abb. 1: Ringe: Benzen-Molekül


Abb. 1: 3D-Strukturen: RNA-Molekül

Leben auf der Basis von Silizium

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Neben Kohlenstoff ist Silizium ein weiteres Element, das kettenförmige Moleküle ausbilden kann.

Mechanisches Leben

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Kurokawa & Murata et al. (1998)
A 3-D self-reconfigurable structure and experiments
Abstract
A three-dimensional self-reconfigurable structure made of identical units is
proposed. Each unit has six arms on the surface of its base cube which can
connect to neighboring units mechanically. By the connection, cubic lattice
structure is formed. A unit can carry its neighbor unit from one node of the
lattice to another by rotating its arm by 90 degrees. Repeating this movement,
the structure can reconfigure itself to realize various 3D structures. General
process of reconfiguration were proposed for this system. Four units were made
and basic motions of self-reconfiguration were verified

New Robot Reproduces on Its Own (2005)
Scientists have created a robot that can replicate itself in minutes. The team
behind the machine says the experiment shows that self- reproduction is not
unique to living organisms The researchers add that the ability could be
harnessed to drive major advances in nanotechnology, the science of the very
small, and may even lead to space colonization by robots. Developed by researchers
at Cornell University in Ithaca, New York, the machine was constructed from cube-
shaped robotic units (modules) that functioned independently. A four-module robot
could assemble an exact replica of itself in just two and a half minutes. Writing
for tomorrow's issue of the science journal Nature, the researchers say the
plastic robotic cubes each contained a microprocessor, a motor, and electromagnets.
The cubes were split diagonally into two halves, allowing the cubes to swivel
to change position or move objects. Each cube was preprogrammed with building
instructions, says Hod Lipson, an assistant professor at Cornell's department of
mechanical and aerospace engineering and department of computing and information
science. "The cubes are aware of contact and release events [with other cubes]
and of the order in which they were assembled," he said. Lipson says the robot
can do little but self-reproduce. But he notes that it would be fairly easy to
add modules with grippers, cameras, or other specialized equipment. The
researcher adds that, while the robot is a relatively simple device, it
strengthens the case of scientists who believe self-reproduction isn't unique to
living organisms and that in the future machines will be able to clone themselves.
If so, the implications for some fields, including nanotechnology and space
exploration, could be huge. "Consider a robotic mission to a remote planet,"
Lipson said. "If a traditional robot is sent and it breaks, the mission is over.
But if modular robots are sent over with a supply of materials, and a fault
happens, they may be able to self-repair."

Recycling Robots
The researcher suggests such robots could adapt to solve problems. If a new,
unforeseen task emerges, a robot might construct a new, more suitable robot from
scratch, and then the new robot will dismantle the old robot," he said. "These
kinds of scenarios, where machines sustain themselves and adapt by consuming and
recycling components, get a little closer to the way biology works." The
prevailing view holds that self-replication is an ability that organisms or
objects either have in full or lack entirely. But Lipson's team theorizes that
self-replication isn't a yes-or-no proposition, but exists at varying degrees.
The researchers present their new robot as an example of this theory. The team
says the extent to which something is self-replicating depends on many factors.
For example, mineral crystals build exact replicas of themselves, but only in a
solution. By contrast, rabbits reproduce themselves less accurately than crystals
do but are less dependent on a specific environment. Through understanding the
principles of self-replication in nature, the team aims to make robots that are
more robust and adaptive. "We are interested in making a practical robot that can
self-reproduce but also do something useful," Lipson said. "We are also interested
in making these machines at microscale." Nanotechnology involves the precise
manipulation of atoms and molecules to create structures around the scale of one
billionth of a meter. Proponents say this fast-expanding field, seen by some as
the next industrial revolution, could potentially change the way almost everything
is manufactured, from medicines to automobiles. More advanced nanotechnology
could see the creation of nanomachines. For instance, so-called nanobots could
be programmed to attack and reconstruct the cells of cancer patients or perform
surgeries a thousand times more precise than currently possible.

Low-Cost Production
A crucial objective of nanotechnology is to make products inexpensively, says
Ralph Merckle, a professor at the Georgia Institute of Technology's College of
Computing in Atlanta. "While the ability to make a few very small, very precise
molecular machines very expensively would clearly be a major scientific achievement,
it would not fundamentally change how we make most products," he said. What's
needed, he says, are huge numbers of robots working together at a molecular scale.
Self-replication is seen as a way of achieving this, using nanobots that can
create copies of themselves to form vast numbers of microscopic assemblers. Such
a scenario has sparked fears among environmentalists and others who have warned
of an apocalyptic "gray goo" event, with self-replicating nanobots possibly
running amok and consuming the planet in a matter of days. Indeed, researchers
at Rice University in Texas recently reported that nanosize buckyballs (soccer
ball-shaped carbon molecules) are water soluble and can interfere with the
respiration of soil microbes. And last year scientists at Southern Methodist
University, also in Texas, reported that those same molecules, often used in
nanotechnology, cause brain damage in certain fish. Prince Charles, heir to the
British throne, is one of the more visible public figures to voice concerns over
the potentially "enormous environmental and social risks" of nanotechnology.
However, proponents counter that the risks associated with self-replicating
machines have been much exaggerated.
"Artificial self-replication is already a risk when it comes to computer viruses
and genetically modified crops," Lipson, the Cornell researcher, said. "I think
that mechanical self-replication is far down the priority list. There are plenty
of other things to worry about before this."

(Courtesy of Cornell University)

Intelligentes Leben

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