by: Nicole Willett
NASA has released information pertaining to the origin of Martian meteorites. The Curiosity Rover has used its Sample Analysis at Mars instrument to analyze the composition of the atmosphere of the Red Planet. The scientists paid close attention to two isotopes of Argon that are present in the atmosphere of Mars. The forms of interest were Argon-36 and Argon-38. There are specific ratios of Argon throughout the solar system. The gaseous ratio on Mars is of particular interest in order to compare the gases trapped inside the meteorites that have landed on Earth and have long been suspected to have originated on the Red Planet. Mars has lost a significant amount of its atmosphere over the history of the solar system. The lighter form of Argon has been lost to space and the heavier form has remained more intact in what is left of the atmosphere. The inert nature of Argon, which is a noble gas, makes it especially relevant to the research of the origin of meteorites from Mars. Being inert means it does not react readily with other gases, so it is stable for a significant amount of time. When taking all of these compelling pieces of evidence into consideration, the team at NASA has concluded that the meteorites are from Mars.
A meteorite is a piece of rock that falls from space to Earth and lands. There are different classifications of meteorites each with a distinct composition of elements. A meteorite tells the geologic history of the body it originates from. There are several classifications of meteorites, the basic categories are: chondrites, stony, stony-iron, and iron. Each category has sub groups and some crossovers and exceptions. Like anything else in science, the more data we gather the more complex the situation gets before we figure it out completely.
The estimates vary greatly for the amount of material that falls to the Earth each year. Some scientists estimate that 37,000 to 87,000 tons of material falls to Earth each year, but of that only 4-5 tons are big enough to land and be collected. However, finding them takes time and patience. Meteorites could conceivably come from anywhere in the solar system. However, of particular interest to scientists are meteorites from Mars. There is an estimated 250-300 pounds of known Martian meteorite material in the hands of scientists and collectors on Earth. Meteorites can be found anywhere on Earth. However, there are places that make it a lot easier to find them, such as desert regions and Antarctica because of the contrast of the light sand or white snow and the dark colored meteorites.
Meteorite ALH 84001 was discovered in 1984 in a region of Antarctica called Allen Hills. This meteorite has gotten more attention than any other in recent history. This little rock from Mars made such a sensation, even President Bill Clinton had to get involved. The Allen Hills meteorite was being studied by Dr. David McKay of NASA. He published an article in the Journal Science in 1996 that claimed meteorite ALH 84001 had micro-fossils inside of it. This sent shock-waves through the scientific community and the world media. Dr. McKay used scanning electron microscope (SEM) technology to image very fine slices of the meteorite. When he saw the images he determined that they were micro-fossils of bacteria that had been preserved in the meteorite from Mars, thus concluding there had been life on the Red Planet in the past and maybe there is life there now.
Immediately other scientists started examining the evidence and some of them came to the conclusion that the results were an artifact of the SEM process and not life. Others stood by McKay’s results and helped to continue his research. To this day there are articles supporting and debunking these results. We may never know if the objects inside the Allen Hills meteorite are microfossils, but we can use other meteorites to extrapolate the data we find to make educated guesses about what the potential for life is in our Solar System.
Falling near Murchison Australia in 1969, the Murchison meteorite was witnessed falling to the ground. It is one of the most studied meteorites in the world. It is not thought to have originated from Mars, but the scientific findings of this space rock pose many questions for scientists, especially astrobiologists. This meteorite has been found to contain many amino acids. Some studies say 15 others say 20 or more. An amino acid is an organic compound. It is a three part grouping of nucleotide bases. These amino acids make up proteins and they encode genes which then make up a DNA strand. To better understand the significance of the amino acid discovery, imagine a nucleotide base as a letter in the alphabet, then group three together to make an amino acid which is like a word in a sentence, next a protein is analogous to a sentence, a gene is like a chapter in a book, and the DNA strand is like an entire book telling the story of an organism. Although the Murchison meteorite is not from Mars, it begs the question, if there are amino acids in meteorites falling from the sky onto Earth, then why wouldn’t there be meteorites falling to Mars with the same organic material? When NASA’s Dr. John Grotzinger explained that the organic compounds recently discovered by the Curiosity Rover may not have originated from Mars, my question is, does it matter where the organic material came from? The organic compounds are there now. Of course this excludes contamination from Earth. Everything on every planet came from somewhere else. We are a collection of material that came from the same swirling cloud of gas and dust. So if organic compounds are on one planet or satellite, then it is logical that all of the bodies in the solar system, and therefore galaxy, have the same ingredients for life. This has also been confirmed by spacecraft that have taken samples from cometary debris which also had amino acids in them. Refer to Blog Issue #4 for Bob Bruner’s Life On Mars In A Box
The Sahara Desert in Africa is where the most recent headline grabbing meteorite was found. This meteorite dubbed NWA 7034 has been found to be a 2.1 billion year old volcanic meteorite from Mars. This was determined by examining the chemical signature of the object. It is nicknamed “Black Beauty” because it has a beautiful dark sheen on its surface. It is said to have been part of a Martian volcanic eruption that sent it off the planet’s surface or by a large meteorite that struck the surface of Mars with enough force to send the rock into the solar system, where it travelled for a couple of billion years until it landed in Africa. When the meteorite was examined it gave off a small amount of water vapor, but compared to other Martian meteorites Black Beauty contained much more water. It also appears to have been altered by an interaction with surface or ground water on the surface of the Red Planet. Scientists are excited because, while they vacillate a Mars Sample Return Mission, they now have a piece of Mars that they can hold in their hands and study here on Earth. They have stated that this is the richest geo-chemical meteorite found to date. Researchers are excited about all of the new discoveries that will be made with the latest addition to the Martian meteorite collection on Earth. ~Stay Tuned!~
[Images: geology.com, Nature.com, Sci-News.com, Museum of Natural History, Fernlea-tripod.com]