Even though its arrival on the surface of comet 67P/Churyumov-Gerasimenko did not go as planned, the accomplishment of the Rosetta probe is immense. We have a probe on the surface that was able to collect 57 hours worth of data before going into hibernation, and a mother ship that will stay with the comet as it moves ever closer to the Sun (the comet’s closest approach will be on August 13 of next year).

What a shame the lander’s ‘docking’ system, involving reverse thrusters and harpoons to fasten it to the surface, malfunctioned, leaving it to bounce twice before it landed with solar panels largely shaded. But we do know that the Philae lander was able to detect organic molecules on the cometary surface, with analysis of the spectra and identification of the molecules said to be continuing. The comet appears to be composed of water ice covered in a thin layer of dust. There is some possibility the lander will revive as the comet moves closer to the Sun, according to Stephan Ulamec (DLR German Aerospace Center), the mission’s Philae Lander Manager, and we can look forward to reams of data from the still functioning Rosetta.

What an audacious and inspiring mission this first soft landing on a comet has been. Congratulations to all involved at the European Space Agency as we look forward to continuing data return as late as December 2015, four months after the comet’s closest approach to the Sun.


Image: The travels of the Philae lander as it rebounds from its touchdown on Comet 67P/Churyumov Gerasimenko. Credit: ESA/Rosetta/Philae/ROLIS/DLR.

A Wave of Discoveries Pending

Rosetta used gravitational assists around both Earth and Mars to make its way to the target, hibernating for two and a half years to conserve power during the long journey. Now we wait for the wake-up call to another distant probe, New Horizons, as it comes out of hibernation for the last time on December 6. Since its January, 2006 launch, the Pluto-bound spacecraft has spent 1,873 days in hibernation, fully two-thirds of its flight time, in eighteen hibernation periods ranging from 36 days to 202 days, a way to reduce wear on the spacecraft’s electronics and to free up an overloaded Deep Space Network for other missions.

When New Horizons transmits a confirmation that it is again in active mode, the signal will take four hours and 25 minutes to reach controllers on Earth, at a time when the spacecraft will be more than 2.9 billion miles from the Earth, and less than twice the Earth-Sun distance from Pluto/Charon. According to the latest report from the New Horizons team, direct observations of the target begin on January 15, with closest approach on July 14.

Nor is exploration slowing down in the asteroid belt, with the Dawn mission on its way to Ceres. Arrival is scheduled for March of 2015. Eleven scientific papers were published last week in the journal Icarus, including a series of high-resolution geological maps of Vesta, which the spacecraft visited between July of 2011 and September of 2012.


Image (click to enlarge): This high-resolution geological map of Vesta is derived from Dawn spacecraft data. Brown colors represent the oldest, most heavily cratered surface. Purple colors in the north and light blue represent terrains modified by the Veneneia and Rheasilvia impacts, respectively. Light purples and dark blue colors below the equator represent the interior of the Rheasilvia and Veneneia basins. Greens and yellows represent relatively young landslides or other downhill movement and crater impact materials, respectively. This map unifies 15 individual quadrangle maps published this week in a special issue of Icarus. Credit: NASA/JPL.

Geological mapping develops the history of the surface from analysis of factors like topography, color and brightness, a process that took two and a half years to complete. We learn that several large impacts, particularly the Veneneia and Rheasilvia impacts in Vesta’s early history and the much later Marcia impact, have been transformative in the development of the small world. Panchromatic images and seven bands of color-filtered images from the spacecraft’s framing camera, provided by the Max Planck Society and the German Aerospace Center, helped to create topographic models of the surface that could be used to interpret Vesta’s geology. Crater statistics fill out the timescale as scientists date the surface.

With a comet under active investigation, an asteroid thoroughly mapped, a spacecraft on its way to the largest object in the asteroid belt, and an outer system encounter coming up for mid-summer of 2015, we’re living in an exciting time for planetary discovery. But we need to keep looking ahead. What follows New Horizons to the edge of the Solar System and beyond? What assets should we be hoping to position around Jupiter’s compelling moons? Is a sample-return mission through the geysers of Enceladus feasible, and what about Titan? Let’s hope Rosetta and upcoming events help us build momentum for following up our current wave of deep space exploration.