Life in Our Solar System

As far as life on other planets is concerned, Mars occupies a special place  

The climate on Mars is not so inimical to life as that on Earth s other direct neighbour, Venus. 

Historical events, such as the discovery of the (hypothetical) canals on Mars, led to strong general interest in Mars in the mid-nineteenth century. 

The phase of science fiction stories about little green men from Mars is hopefully over, and the question can only be are there, or were there ever, real living systems there, or can we find traces of precursors of life in the form of biomolecules  

Free water, the essential precondition for life as we know it, has recently been detected on Mars images taken by the high resolution stereo camera (HRSC) on board ESA s Mars Express spacecraft show a patch of water ice on the floor of an unnamed crater near the Martian north pole. Geomorphic studies indicate that the surface of Mars can be divided into two types (Jaumann et al 2002)  

---

Life in our Solar System could have started rapidly if the Panspermia Hypothesis is correct and life was seeded to Earth (and Mars and Europa ) from outside, or it may have taken hundreds of millions of years. At this time, only the crudest boundaries can be placed on the time for life to develop or the survival time for life after environmental conditions become hostile, but it may be on the order of hundreds of millions of years. 

In the search for life in our Solar System, all of the above important resources for life, constraints for life, biosignatures, and geosignatures are appropriate criteria. In the search for life beyond our Solar System, attention should focus on (1) energy (especially solar) sources, (2) liquid water, (3)... 

Earlier, we examined the possibility that life could ultimately be curtailed throughout the Universe by the laws of thermodynamics. Whether this is true or not depends on the validity of certain assumptions (Sect. 6.2). In any case, such a termination would be tens or hundreds of billions of years into the future, if there is an open, forever-expanding Universe. Of closer concern is our Solar System, where the time lines for life are shorter, but still billions of years into the future (Sect. 6.3). It seems a foregone conclusion that life in our Solar System will someday be terminated. 

How can scientists collect experimental evidence about possible life on another planet Sending astronauts to see for themselves is impractical at our current level of technology. Nevertheless, it is possible to search for life on other worlds without sending humans into space. In the late 1970s, NASA s Viking spacecraft lander collected a sample of dirt from Mars, the planet in our solar system most like Earth. The sample showed no signs of life. Nevertheless, speculation continues about Martian life. 

Of the three extraterrestrial targets in our solar system, the Saturnian moon Titan is the least likely to provide signs of life. To quote Christopher McKay from the NASA Ames Research Center, Titan is an interesting world. For example, its organic haze layer could be an example of the prebiotic chemistry which led to life on Earth . Direct links to extraterrestrial life have not, however, yet been found, as water (one of the main preconditions for life) has not been detected on Titan, apart from traces of water vapour in the higher layers of the Titanian atmosphere (Brack, 2002). 

There are several bodies of information that feed into our understanding of stellar nucleosynthesis. We will start with a discussion of the classification of stars, their masses and mass distributions, and their lifetimes. From this information we can assess the relative importance of different types of stars to the nucleosynthesis of the elements in our solar system and in the galaxy. We will then discuss the life cycles of stars to give a framework for the discussion of nucleosynthesis processes. Next, we will review the nuclear pathways... 

In Chap. 6, we first discuss a search strategy for life in the Universe and then speculate about future life on Earth, in our Solar System, and in the Universe. 

If the global structures of terran life reflect origins, we must turn to models of early Earth and consider its chemistry in an effort to guess the potential for life in the solar system. Other planets and moons in our solar system have had histories different from Earth s. We would be called on to creatively define chemistries that might have originated in the early histories of those other bodies. 

Beyond our planet, technology has enabled us to travel to the moon and beyond. By analyzing the percent composition of the rocks and minerals found on the moon and Mars and comparing them to those on earth, scientists can begin to gather more information on whether life can exist on planets in our solar system. 

Current evidence indicates that all major bodies in our solar system originated about the same time, approximately 4.6 Ga ago. The oldest rocks taken from the surface of the Moon and meteorites found on Earth are about 4.5 Ga old. The Moon, Mercury, Venus, and Mars have cratered surfaces that appear to be the result of the same type of meteoric activity that produced craters on Earth. The early atmosphere on Earth was probably similar to those found today on nearby planets on which life did not evolve. Hence, we can use information about those planets to help us infer the nature of the conditions on Earth under which life presumably evolved. 

Now the occultist has divided matter, seen and unseen, into seven principles or planes, and of these the fifth principle, or Quintessence, corresponds to Science s Ether of Space. If we are willing to admit that there is truth in this statement, then we may begin to see that alchemy is based on absolute Law. All the forces of our scientists have originated in the Vital Principle, that one Collective Life of our Solar System, which life is a part of, or rather one of the aspects of, the One Universal Life. 

Nevertheless, at the current state of the science, only the known fossil record can provide clear-cut evidence of the antiquity of life on Earth, yielding a minimum age for life s existence and a basis for extrapolation as to when life may have actually emerged. The techniques used to investigate this problem have bearing on the broader issue of whether life once existed (or may now exist) elsewhere in our solar system, because the same questions will be asked and similar techniques applied in the search for evidence of past Ufe in rock samples from other planetary bodies. 

The potential that life can exist in a subsurface realm, independent of photosynthetic productivity, has raised the possibility that habitable niches may exist elsewhere in our solar system [84]. As defined by the long-term stability of liquid water, the Earth is at present the only body in the solar system capable of supporting a surface biosphere. Any biosphere elsewhere in the solar system would therefore be confined to the deep subsurface. Specifically, attention has been focused on Mars and Europa, both of which may support... 

In my opinion. Titan is the best candidate in our solar system for the presence of extraterrestrial life because it has the three phases of matter flowing into each other. In fact, we may already have evidence in hand that life exists there, although from this far away, it s hard to tell. 

Earth s atmosphere is unique in our solar system. Other planets and some moons have an atmosphere, but Earth s atmosphere is the only one of which we are aware that can support life as we know it. (Life may exist elsewhere in the solar system—and the search for extraterrestrial life is part of many space missions—but the fact remains that the presence of life outside of Earth s biosphere has not been discovered.)... 

No traces of lines of predicted energy, nor its daughters were found at all. Obtained minimum detectable activity for this nuclide was estimated to be approx. 15 uBq/g, which gives the upper limit for Darmstadtium concentration as low as 10 g/g. Despite a lack of any known natural processes, which can produce super-heavy nuclides in our Solar System or near it, which might lead to its presence in particular in stratosphere, a search for them seems to be still worth the efforts because of predicted long half-life times and thus nonzero probability of their existence. 

Water is one of the basic elements for life. It is even assumed that the evolution of life is only possible if there is liquid water present. A water molecule has some remarkable properties that make it quite unique in the universe. In the first chapter of this book we will review these basic properties of water and the role of water on Earth. All ancient civilizations realized the importance of water and their cities were constructed near great reservoirs of water. But is water unique on Earth Do we find water elsewhere in the solar system, on extrasolar planetary systems or in distant galaxies We will start the search for the presence of extraterrestrial water in our solar system. Surprisingly enough it seems that water in some form and sometimes in only minute quantities is found on any object in the solar system. Even on the planet nearest to the Sun, Mercury, there may be some water in the form of ice near its poles where never the light of Sun heats the surface. And there are objects in the solar system that are made up of a large quantity of water in terms of their mass, like comets and several satellites of the giant planets. 

The presence of water as solid, liquid, and gas is a feature that makes Earth unique in the solar system and that makes life possible as we know it. The transport of water and the energy exchanged as it is converted from one state to another are important drivers in our weather and climate. One of the key missions is to develop a better understanding of the global water cycle at a variety of scales so that we can improve model forecasts of climate trends,... 

Although the terms exobiology and astrobiology really mean the same thing, astro-biology , introduced by NASA in 1995, has become the one of choice. This branch of science reaches from cosmochemistry via biogenesis to all the other themes involving research on traces of life (of whatever sort) on planets and on moons, both within and outside our solar system. 

---