Cassini sends in­tel on Ti­tan’s lakes

The Star Malaysia - Star2 - - SCIENCE -

NASA’S Cassini mis­sion flew past Ti­tan early last Wed­nes­day, suc­cess­fully com­plet­ing a com­plex ma­noeu­vre that will help sci­en­tists bet­ter un­der­stand one of the so­lar sys­tem’s most in­trigu­ing moons.

Be­gin­ning around mid­night, a team of sci­en­tists and en­gi­neers guided the space­craft into an or­bit that al­lowed them to bounce a ra­dio sig­nal off the sur­face of Ti­tan to­ward Earth, where it was re­ceived by a land-based te­le­scope ar­ray 1.6 bil­lion km away.

“We are es­sen­tially us­ing Ti­tan as a mir­ror,” said Es­sam Marouf of San Jose State Univer­sity and a mem­ber of the Cassini ra­dio sci­ence team. “And the na­ture of the echo can tell us about the na­ture of Ti­tan’s sur­face, whether it is liq­uid or solid, and the phys­i­cal prop­er­ties of the ma­te­rial.”

Saturn’s moon Ti­tan is the sec­ond largest moon in the so­lar sys­tem af­ter Jupiter’s moon Ganymede, and in some ways, it’s one of the most Earth-like bod­ies we have en­coun­tered. Like Earth, it has a thick at­mos­phere, and it is the only other world we know of that has a sys­tem of liq­uid lakes and seas on its sur­face. How­ever, un­like Earth, its sur­face is far too cold to sus­tain liq­uid wa­ter.

Sci­en­tists have hy­poth­e­sised that Ti­tan’s fa­mous lakes and seas are made of liq­uid meth­ane or eth­ane, but Marouf ex­plains that those in­fer­ences are mostly based on the fact that meth­ane and eth­ane would take on a liq­uid state in the con­di­tions on Ti­tan, rather than di­rect ob­ser­va­tion.

“There is no re­ally di­rect mea­sure­ment that tells us what they are ex­actly,” he said. “If the data from this morn­ing is good enough, it will tell us what these liq­uids re­ally are.”

Marouf gath­ered with other mem­bers of Cassini’s ra­dio sci­ence team in a con­trol room at the Jet Propul­sion Lab­o­ra­tory in La Canada Flin­tridge near down­town Los Angeles, watch­ing as the new data streamed in to a ra­dio te­le­scope ar­ray in Aus­tralia.

He said they could not an­a­lyse the data in real time, but were able to tell that the sig­nal was clear enough to give them some­thing to work with.

Cassini per­formed a sim­i­lar ex­per­i­ment on Saturn’s sur­face on May 17 that was also a suc­cess. That time, the re­searchers were able to col­lect in­for­ma­tion from two of the largest bod­ies of liq­uid on Ti­tan: Ligea Mare and Kraken Mare.

This time, Cassini bounced its ra­dio sig­nal off an area be­tween the two seas where radar im­ages had found smaller liq­uid re­gions sim­i­lar to rivers, lakes and chan­nels on Earth.

“This kind of ex­per­i­ment takes a metic­u­lous kind of prepa­ra­tion to first know where to look, and then de­sign the ma­noeu­vres,” Marouf said. “There are many pieces that have to work flaw­lessly to end up with the data.”

He said the team hopes to share its early re­sults soon. — Los Angeles Times/McClatchy-Tri­bune In­for­ma­tion Ser­vices

an artist’s ren­der­ing of Cassini’s in­ser­tion in Saturn’s or­bit. The space­craft has sent back valu­able data on two ma­jor lakes on the planet’s moon Ti­tan, which could help sci­en­tists de­ter­mine their com­po­si­tion. — nasa

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