Are We All Actually Martians?
“The evidence seems to be building that we are actually all Martians; that life started on Mars and came to Earth on a rock”
Prof Steven Benner, Westheimer Institute for Science and Technology
Where do we come from? One of the most hotly debated questions in science and philosophy centres around the origin of life itself. Even defining what life is can be controversial. Scientists often begin tackling this question by investigating the chemical building blocks of life – peptides, DNA and RNA – and how, and where, these materials are assembled. Experiments that attempted to replicate the synthesis of these biomolecules, by recreating conditions thought to be like the young Earth, have failed to produce substantial results.
Partly because of these poor results, many hypotheses assert that these essential ingredients may have been delivered to the early Earth on meteorites and comets originating from other parts of the Solar System. Figuring this out is incredibly difficult because the early Earth was so violently active that it effectively erased the entire early fossil record.
A recent conference presentation has sparked a lot of media attention: BBC News, The Guardian, The Telegraph, Sky News and many more latched onto the story. The crux of this story is the assumption that conditions on Mars were much more conducive to producing ribose – a key component of RNA – than those on Earth. It is commonly believed that RNA formed before DNA, and was a vital step towards producing the first living entities which were the common ancestor to all life on Earth.
To assess these claims, we must rely on secondary sources – i.e., news articles – as no paper has been peer-reviewed or published and the claims were made during a conference presentation which the general public has no access to, apart from a vague abstract (PDF).
The story centres around the assumed abundance of certain minerals on early Earth and Mars which have been linked with biomolecule synthesis. Boron-containing minerals are thought to facilitate the formation of carbohydrate rings, which can subsequently be converted to ribose in the presence of highly-oxidised molybdenum minerals. Ribose is a simple sugar molecule which, when linked by phosphate groups and appended with nucleobases, forms the backbone of RNA. In other words, Ribose is one of the three major components of RNA.
So what are thought to be the differences between early Earth and Mars? On Mars, conditions were thought to be very oxidising, so metals in mineral existed in their highly oxidised state, for example, rust is highly oxidised iron which contributes to the Red Planet’s famous hue. The opposite was thought to be the case on the young Earth, and so molybdenum would not be in the high oxidation states necessary to catalyse Ribose formation from carbohydrates. Available boron levels are also thought to have been lower on Earth than Mars, and so less was available to facilitate carbohydrate formation. These arguments form the basis of the latest “life on Mars” hypothesis.
The press have predictably focused on the “we are Martians” angle, which is a blunt overstatement. Even if Mars was our source of Ribose, can we really consider ourselves descended from a non-replicating simple Martian sugar molecule? Should we consider a Rolls Royce Japanese if its ball bearings were made in Tokyo? Ribose is one precursor of one component of the mechanisms of life, and cannot be considered “life” itself.
Additionally, there are many assumptions associated with this news item, including:
• Mars was highly oxidising in the past
• Boron and molybdenum were more abundant and available on early Mars
• RNA was the vital component of early life
• Ribose would survive on the proposed highly oxidising surface of Mars
• Boron and molybdenum minerals are the only catalysts for producing Ribose from simple precursors
• Ribose would survive the interplanetary journey from Mars to Earth and the high temperatures and pressures produced by atmospheric friction and impact on Earth
Assumptions are always necessary when studying the origin of life, as we currently do not possess enough information on the conditions of the early Earth and Mars – we still send Rovers like Curiosity to Mars to study its geology, surface chemistry and radiation levels. We are also far from understanding the processes that created the complex molecules of life from the simple precursors available. This article, while adding to our current discourse on the matter, has been blown out of proportion by media coverage looking to pique public interest.
Additional hypotheses and studies like this are always welcome, but we at Research the Headlines are waiting for the peer-reviewed publication on this subject before drawing any more conclusions.