A malfunction of the Philae comet landers two anchoring harpoons designed to help secure the 100 kg lander to the surface of comet 67P/Churyumov-Gerasimenko may have inadvertently saved the European Space Agencys (ESA) Rosetta mission probe from being tossed back into space, Rosetta Project Scientist Matt Taylor told Forbes.

Taylor reckons that because the comet now appears to have a harder-than-expected icy subsurface, if the harpoons had deployed they may never have been able to penetrate deep enough to anchor.

He also notes that a small top-mounted gas thruster designed to exert a downward force during the last crucial moments before touchdown also seems to have failed. Thus, the combination of an impenetrable subsurface and a malfunctioning lander thruster might not have been enough to stymie the recoiling force from the two harpoons. Even so, Taylor emphasizes that the Rosetta team wont know for certain if this would have been the case until all the lander data are fully analyzed. At present, the lander seems to be sitting in only partial sunlight next to a wall of ice, atop perhaps as much as half a foot of dusty hydrocarbon soot.

This montage comprises four individual NAVCAM images taken from 30.1 km from the centre of Comet 67P/Churyumov-Gerasimenko on 26 November 2014. Credit: ESA

There appears to be a porous dust layer on the surface, with a cigarette ash-type feel to it, said Taylor. When you put these images out in grayscale, you lose the fact that this comet is in fact a very dark object.

After being hamstrung by a final landing spot that appears to suffer from limited sunlight, Philae was able to take more than sixty hours of science data from the surface before its batteries ran down and the probe put itself into hibernation on November 15th. If the lander had landed in a well-illuminated spot, its nominal mission of sniffing, sampling, hammering and drilling might have lasted until March of 2015.

We have data from magnetic fields, gas spectrometers which have sniffed the comet at different locations, as well as measurements of temperatures and surface quantities, said Taylor.

Despite Philaes premature hibernation, ESAs successful landing on a comet some 510 million km from Earth is a signal achievement for the ages.

Comets are a crucial part of the primordial detritus left over from the earliest formation of our solar system. And because what looks like comet reservoirs have also been spotted circling alien solar systems, planetary scientists think that comets are likely to also be ubiquitous throughout our Milky Way galaxy.

How well we understand them is vital in understanding not only how our own solar system has evolved over its 4.56 billion-year history, but how solar systems throughout the galaxy might have also evolved and delivered so-called volatiles, such as water to Earthlike planets both here and elsewhere.

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Harpoon Malfunction May Have Saved ESA's Philae Comet Lander