R. Erickson

The above images are Digital Elevation Models (DEM) depicting the topography of Mars and Earth, respectivly. Life is considered a characteristic of something that preserves, furthers or reinforces its existence in the given environment. Do either of the images show indications of life through this lense?

Is there a topographic signature of life (Dietrich and Perron 2006)

In 2006, Dr. William Dietrich and Dr. Perron Landscapes are shaped by the uplift, deformation and breakdown of bedrock and the erosion, transport and deposition of sediment. Life is important in all of these processes. Over short timescales, the impact of life is quite apparent: rock weathering, soil formation and erosion, slope stability and river dynamics are directly influenced by biotic processes that mediate chemical reactions, dilate soil, disrupt the ground surface and add strength with a weave of roots. Over geologic time, biotic effects are less obvious but equally important: biota affect climate, and climatic conditions dictate the mechanisms and rates of erosion that control topographic evolution. Apart from the obvious influence of humans, does the resulting landscape bear an unmistakable stamp of life? The influence of life on topography is a topic that has remained largely unexplored. Erosion laws that explicitly include biotic effects are needed to explore how intrinsically small-scale biotic processes can influence the form of entire landscapes, and to determine whether these processes create a distinctive topography.

What is Life? - A Unique Perspective

The existance of a topographical signature of life is Thermodynamics tells us matter can neither be created nor destroyed; it can only change states relative to the system in question. Of course, there are many definitions of a system, , life did not simply zap into existance, or did it? If one places a "simplistic", over-arching description of life how events within living organisms can be accounted for by the laws of physics and chemistry. He argued that life maintains order by continuously extracting energy from its environment to counteract the natural tendency toward disorder described by the second law of thermodynamics, a concept he described as "negative entropy" or "feeding on negative entropy". This process, which he termed metabolism, involves activities like eating, drinking, breathing, and assimilating to maintain a stable internal state

Biosignatures

A potential biosignature is a substance or structure that might have a biological origin but requires more data or further study before reaching a conclusion about the absence or presence of life. As the name indicates, a biosignature is a sign of life. Oftentimes, when we think about biosignatures, we think about signs of past life, usually preserved in the rock record, sometimes preserved in atmospheric gases or anything like that. But in general, what it is, is it's an indication not necessarily of a particular living thing at this moment, but a sign that there was life in an environment or in a place sometime in the past, Sometimes when we think about potential biosignatures, we're also talking about something that's different than how we think of life on our planet. When we're thinking about life on other planets, that can be different enough from life on our planet that we have to eliminate more possibilities. We have to think more deeply about the chemistry, about the geological processes on those other planets, as a way to make sure that something that we see is truly an indication of life somewhere else.

Every possible biosignature is associated with its own set of unique false positive mechanisms or non-biological processes that can mimic the detectable feature of a biosignature. An important example is using oxygen as a biosignature. On Earth, the majority of life is centred around oxygen. It is a byproduct of photosynthesis and is subsequently used by other life forms to breathe. Oxygen is also readily detectable in spectra, with multiple bands across a relatively wide wavelength range, therefore, it makes a very good biosignature. However, finding oxygen alone in a planet's atmosphere is not enough to confirm a biosignature because of the false-positive mechanisms associated with it. One possibility is that oxygen can build up abiotically via photolysis if there is a low inventory of non-condensable gasses or if the planet loses a lot of water. Finding and distinguishing a biosignature from its potential false-positive mechanisms is one of the most complicated parts of testing for viability because it relies on human ingenuity to break an abiotic-biological degeneracy, if nature allows.

Revisiting the Topographic Signature of Life

We identified a series of hypotheses that might link biological presence to measurable differences in topographic form or signal. Alongside these hypotheses, we developed a communal list of exploratory questions to identify knowledge gaps and promising research directions. The relationships between life, topography, and climate are highly context dependent, requiring numerous disciplines to properly explain why the processes in an area occur (Dahlman and Renwick, 2014). For example, vegetation may suppress erosion in some systems but enhance it in others. Rain, which entices growth, has large erosion impacts on bedrock over time while attributing to vegetative erosion or support of topographical features. Some of the most pressing questions we found included:

The availability of appropriate data (e.g., LiDAR, InSAR and other high-resolution sources) now varies widely due to improvements made to geographic informational databases. Fine spatial scales at which different processes operate are now made possible. In response, we began thinking about how to utilize this powerful technology in meaningful ways. While no universal model applies, we identified a range of useful approaches to identify numerous actionable studies:

I had sugegsted we look near underwater volcanoes; extremophiles can be seen thriving in extreme conditions no human can live. In addition, not all volcanoes settle post-erruption in the same manner. There is seems to be a limiting constraint that causes volcanic activity to settle into a shape independently of those on Mars. Can life be this limiting constraint, or is this simply representative of the differences in mass between Mars and Earth. Microbes often interact with geochemical processes, leaving features in the rock record indicative of biosignatures. For example, bacterial micrometer-sized pores in carbonate rocks resemble inclusions under transmitted light, but have distinct sizes, shapes, and patterns (swirling or dendritic) and are distributed differently from common fluid inclusions. Can these be seen from space, and futher utilized to determine non-Earthly biosignatures?