Shooting Stars: Comet-chaser Rosetta to feature at the inaugural World Science Festival Brisbane.


By Samuel Mortimer

For thousands of years, from the Bronze age through to the more modern discoveries of people such as Galileo, Einstein and Carl Sagan, space has been the catalyst fuelling an innate human desire to explain and explore the universe we live in. It was a desire that reached fever pitch during the historic multi-national race to the moon in the 1960s, and one that continues to be stoked with projects like the International Space Station today. Just last week NASA astronaut Scott Kelly touched down in Russia after spending 340 days on-board the ISS – the longest stint recorded in more than 20 years.

Despite the substantial advances in technology post moon-landings, the still very real dangers involved in human spaceflight coupled with declining governmental budgets, have meant the last forty-odd years of space exploration have primarily been the domain of unmanned rovers and probes. This is where the pioneering efforts of dedicated NASA and European Space Agency scientists comes in.

Space enthusiasts will be given a behind the scenes look at the trials, tribulations and key discoveries of the ESA’s Rosetta mission at the inaugural World Science Festival Brisbane, beginning this Wednesday, March 9 in association with Queensland Museum. The Festival calls itself a “big-thinking, high energy, supercharged celebration of science” featuring 100 events about all things science, both free and ticketed, across the five days and four nights to Sunday.

When you are talking about sending a probe to orbit a comet, funding issues merely scratch the surface of a mission’s complexity.

Rosetta takes a selfie with Comet 67P in September of 2014.

Rosetta takes a selfie with Comet 67P – September 2014.
Source: ESA

Overcoming a litany of logistical challenges, the Rosetta probe and companion lander Philae survived the budget razor-gangs of the 1990s and lived to tell us the tale of comet 67P/Churyumov-Gerasimenko.

After launching on the back of an Ariane 5 rocket in 2004, Rosetta made an epic 10-year journey across the solar system involving three gravity-assist manoeuvres around Earth and one perilously close around Mars. It hurtled the 11.4 billion kilometres toward the comet at a staggering peak speed of 55,000 km/hour, matching that of the comet on approach.

After careful manoeuvring by ESA scientists, controlling remotely from the European Space Operations Center in Darmstadt, Germany, the dynamic duo made history in August 2014 as the first probe and lander to successfully enter orbit around a comet. The mission has returned a wealth of scientific data in the year and a half since, though not entirely without incident.

The Philae lander portion was deployed as planned in November 2014, making a seven hour decent to the surface. The pace was slow due to the comets small size and density, making its gravitational influence, according to ESA, “several hundred thousand times” weaker than Earth’s.

Although Philae was equipped with harpoons to anchor it to the surface of 67P, they unfortunately did not fire, causing the lander to tumble across the comet over several hours in near zero gravity. Despite this, Philae managed to complete 80% of its main scientific objectives over 57 hours until its batteries depleted.

Philae's path across the comet surface.

Philae’s path across the comet surface. Source: ESA

ESA personified Philae by posting ‘first person’ updates from it’s very own Twitter handle, making the search for the stricken lander a somewhat emotional experience for thousands following online.

Many attempts were made to re-establish contact with the lander, and although ESA briefly re-established contact at one stage, scientists finally conceded last month that the lander was facing “eternal hibernation”.

Despite the loss of Philae the Rosetta mission has been an overwhelmingly successful venture, smashing numerous ‘firsts’ in space exploration.

Among the most exciting of those achievements, Rosetta is the first spacecraft to provide in-situ data about the changes a comet nucleus experiences as it nears the sun, recording data using its 11 instruments as 67P reached perihelion last August – its closest distance to the sun.

The mission is now in its extended phase, which ESA plans to terminate by carefully landing the probe on the comet by the end of September.

The triumphs, discoveries and difficulties of the mission are set to be the focus of two behind-the-scenes talks at the World Science Festival featuring the ESA’s Senior Advisor in Science and Robotics, Mark McCaughrean. On Thursday night, Rosetta Rendezvous will feature Mr McCaughrean in an informal discussion exploring the challenges and risks involved in the mission. Rosetta’s latest discoveries will be the focus of Friday’s event, Chasing Down the Comet, with Mr McCaughrean, NASA’s Rosetta Project Manager, Artur Chmielewski and CSIRO astronomer and science writer, Lisa Harvey-Smith.

For more information about the festival schedule or to purchase tickets to special events such as the Rosetta talks, check out the World Science Festival website.


Five interesting facts you might not know about the Rosetta Mission:

Rosetta originally had another target

Rosetta’s initial target was comet 46P/Wirtanen, but the original 2003 launch date was scratched after the catastrophic failure of an Ariane 5 rocket – the type set to carry the mission. The delay meant 46P was no longer a viable target. Rosetta finally launched with it’s new destination plan in 2004.

67P/Churyumov-Gerasimenko stinks

The Rosetta Orbiter Sensor for Ion and Neutral Analysis (ROSINA) instrument detected some particularly potent molecules emanating from 67P – hydrogen sulphide, ammonia, formaldehyde and cyanide just to name a few. Just as well it doesn’t have an atmosphere.

67P’s water is not like ours

The ROSINA instrument also discovered that water vapour coming from the comet had a significantly different ratio of deuterium-to-hydrogen than water found on Earth. The ratio is key to figuring out which part of our solar system the water in Earth’s oceans originated.

“A geologist’s playground”

Geographical analysis of the comet revealed a remarkable diversity across the comet surface. Extremely porous, 67P’s surface ranges from smooth terrains of dust that slowly evolve, to “accumulation basins” full of boulders of all sizes as a result of erosion. Boulders appear to sink overtime as fractures below the surface of the comet release under pressure.

Rosetta was not the first comet mission for the European Space Agency

In 1986, ESA’s Giotto probe flew within 600km of Halley’s Comet, returning spectacular images and data from a vantage point our ancestors could only have dreamed of. Dust from the nucleus of the comet pummelled the spacecraft at 68km/sec, destroying the camera and eroding instrument shielding. Halley’s Comet won’t be back in our neighbourhood until 2061.