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Title: Atmospheric Constraints on the Surface UV Environment of Mars at 3.9 Ga Relevant to Prebiotic Chemistry
Author: Sukrit Ranjan, Robin D. Wordsworth, Dimitar D. Sasselov

Recent findings suggest Mars may have been a clement environment for the emergence of life, and may even have compared favourably to Earth in this regard. These findings have revived interest in the hypothesis that prebiotically important molecules or even nascent life may have formed on Mars and been transferred to Earth. UV light plays a key role in prebiotic chemistry. Characterizing the early Martian surface UV environment is key to understanding how Mars compares to Earth as a venue for prebiotic chemistry.
Here, we present two-stream multi-layer calculations of the UV surface radiance on Mars at 3.9 Ga, to constrain the surface UV environment as a function of atmospheric state. We explore a wide range of atmospheric pressures, temperatures and compositions, corresponding to the diversity of Martian atmospheric states consistent with available constraints. We include the effects of clouds and dust. We calculate dose rates to quantify the effect of different atmospheric states on UV-sensitive prebiotic chemistry.
We find that for normative clear-sky CO2-H2O atmospheres, the UV environment on young Mars is comparable to young Earth. This similarity is robust to moderate cloud cover: thick clouds (tau>100) are required to significantly affect the Martian UV environment, because cloud absorption is degenerate with atmospheric CO2. On the other hand, absorption from SO2, H2S, and dust is nondegenerate with CO2, meaning if they can build up to high levels, surface UV fluence will be suppressed. These absorbers have spectrally variable absorption, meaning that their presence affects prebiotic pathways in different ways. In particular, high SO2 environments may admit UV fluence that favours pathways conducive to abiogenesis over pathways unfavourable to it. However, better measurements of the spectral quantum yields of these pathways are required to evaluate this hypothesis definitively.

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Mars has macroweather too

Mars has the same three-part pattern of atmospheric conditions as Earth, finds a new study by researchers at UCL and McGill University. This includes weather, which changes day-to-day due to constant fluctuations in the atmosphere; climate, which varies over decades and a third regime called macroweather, which describes the relatively stable regime between weather and climate.
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NASA Spacecraft Reveal Largest Crater in Solar System

New analysis of Mars' terrain using NASA spacecraft observations reveals what appears to be by far the largest impact crater ever found in the solar system.
NASA's Mars Reconnaissance Orbiter and Mars Global Surveyor have provided detailed information about the elevations and gravity of the Red Planet's northern and southern hemispheres. A new study using this information may solve one of the biggest remaining mysteries in the solar system: Why does Mars have two strikingly different kinds of terrain in its northern and southern hemispheres? The huge crater is creating intense scientific interest.



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  First Mars Express gravity results plot volcanic history

Five years of Mars Express gravity mapping data are providing unique insights into what lies beneath the Red Planets largest volcanoes. The results show that the lava grew denser over time and that the thickness of the planet's rigid outer layers varies across the Tharsis region.
The measurements were made while Mars Express was at altitudes of between 275330 km above the Tharsis volcanic bulge during the closest points of its eccentric orbit, and were combined with data from NASAs Mars Reconnaissance Orbiter.
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Mars' motion in 2012, its retrogradation loop, ecliptic & constellations by Robert von Heeren



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Mars used to be warmer and wetter than it is now

US researchers have determined the surface temperature of early Mars for the first time, providing evidence consistent with a warmer and wetter Martian past.
By analysing carbonate minerals in a four-billion-year-old meteorite that originated near the surface of Mars, scientists at the California Institute of Technology determined that the minerals formed at about 18 degrees Celsius (64 degrees Fahrenheit).
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Northern Spring on Mars begins on the 13th September, 2011.

 

Spring time on mars



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Jupiter's Early Migration Could Explain Mars's Small Size

The migration of giant planets has been invoked to explain a number of features of planetary systems, such as the uneven spacing among the objects of the Asteroid Belt in our solar system. Migration would also explain the huge planets in other planetary systems known as "hot Jupiters" that orbit extremely close to their host stars, far closer than where they could have plausibly formed.
Now a new study, published online June 5 in Nature, demonstrates that a peculiar migration of Jupiter - first inward, then outward - could account for Mars's relatively small size.
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For Mars, rapid formation stunted growth

Mars developed in as little as two to four million years after the birth of the solar system, far more quickly than Earth, according to a new study published in the May 26 issue of the journal Nature. The red planets rapid formation helps explain why it is so small, say the studys co-authors, Nicolas Dauphas at the University of Chicago and Ali Pourmand at the University of Miami (Fla).
Mars probably is not a terrestrial planet like Earth, which grew to its full size over 50 to 100 million years via collisions with other small bodies in the solar system, said Dauphas, an associate professor in geophysical sciences. Mars instead is a planetary embryo that never developed into a full-fledged planet.
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Mars: Red Planet's Rapid Formation Explains Its Small Size Relative to Earth

Mars developed in as little as two to four million years after the birth of the solar system, far more quickly than Earth, according to results of a new study published in this week's issue of the journal Nature.
The red planet's rapid formation helps explain why it is so small, say the study's co-authors, Nicolas Dauphas at the University of Chicago and Ali Pourmand at the University of Miami.
Their research was funded by the National Science Foundation (NSF).
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