Wa­ter dis­cov­ered in at­mos­phere of hab­it­able ex­o­planet

Kuwait Times - - Front Page -

PARIS: Wa­ter has been dis­cov­ered for the first time in the at­mos­phere of an ex­o­planet with Earth-like tem­per­a­tures that could sup­port life as we know it, sci­en­tists re­vealed yes­ter­day. Eight times the mass of Earth and twice as big, K2-18b or­bits in its star’s “hab­it­able zone” at a dis­tance - nei­ther too far nor too close - where wa­ter can ex­ist in liq­uid form, they re­ported in the jour­nal Na­ture As­tron­omy.

“This planet is the best can­di­date we have out­side our so­lar sys­tem” in the search for signs of life, co-au­thor Gio­vanna Tinetti, an as­tronomer at Univer­sity Col­lege Lon­don, told AFP. “We can­not as­sume that it has oceans on the surface but it is a real pos­si­bil­ity.” Of the more than 4,000 ex­o­plan­ets de­tected to date, this is the first known to com­bine a rocky surface and an at­mos­phere with wa­ter.

Most ex­o­plan­ets with at­mos­pheres are gi­ant balls of gas, and the hand­ful of rocky plan­ets for which data is avail­able seem to have no at­mos­phere at all. Even if they did, most Earth-like plan­ets are too far from their stars to have liq­uid wa­ter or so close that any H2O has evap­o­rated. Dis­cov­ered in 2015, K2-18b is one of hun­dreds of so­called “su­per-Earths” - plan­ets with less than ten times the mass of ours-spot­ted by NASA’s Ke­pler space­craft.

Fu­ture space mis­sions are ex­pected to de­tect hun­dreds more in the com­ing decades.

“Find­ing wa­ter in a po­ten­tially hab­it­able world other than Earth is in­cred­i­bly ex­cit­ing,” said lead-au­thor An­ge­los Tsiaras, also from UCL. “K2-18b is not ‘Earth 2.0’,” he said. “How­ever, it brings us closer to an­swer­ing the fun­da­men­tal ques­tion: Is the Earth unique?”

Work­ing with spec­tro­scopic data cap­tured in 2016 and 2017 by the Hub­ble Space Tele­scope, Tsiaras and his team used open-source al­go­rithms to an­a­lyze the starlight fil­tered through K2-18b’s at­mos­phere. They found the un­mis­tak­able sig­na­ture of wa­ter vapour. Ex­actly how much re­mains un­cer­tain, but com­puter mod­el­ling sug­gested con­cen­tra­tions be­tween 0.1 and 50 per­cent.

By com­par­i­son, the per­cent­age of wa­ter vapor in Earth’s at­mos­phere varies be­tween 0.2 per­cent above the poles, and up to four per­cent in the trop­ics. There was also evidence of hy­dro­gen and he­lium as well. Ni­tro­gen and meth­ane may also be present but with current tech­nol­ogy re­main un­de­tectable, the study said. Fur­ther re­search will be able to de­ter­mine the extent of cloud cov­er­age and the per­cent­age of wa­ter in the at­mos­phere.

Wa­ter is cru­cial in the search for life, in part be­cause it car­ries oxy­gen. “Life as we know is based on wa­ter,” said Tinetti. K2-18b or­bits a red dwarf star about 110 light years dis­tant - a mil­lion bil­lion kilo­me­tres - in the Leo con­stel­la­tion of the Milky Way, and is prob­a­bly bom­barded by more de­struc­tive ra­di­a­tion than Earth.

“It is likely that this is the first of many dis­cov­er­ies of po­ten­tially hab­it­able plan­ets,” said UCL as­tronomer Ingo Wald­mann, also a co-au­thor. “This is not only be­cause su­per-Earths like K2-18b are the most com­mon plan­ets in our galaxy, but also be­cause red dwarfs - stars smaller than our Sun - are the most com­mon stars.”

The new gen­er­a­tion of space-based star gaz­ing in­stru­ments led by the James Webb Space Tele­scope and the Euro­pean Space Agency’s ARIEL mis­sion will be able to de­scribe ex­o­planet at­mos­pheres in far greater de­tail. ARIEL, slated for a 2028 launch, will can­vas some 1,000 plan­ets, a large enough sam­pling to look for pat­terns and iden­tify out­liers. “Over 4,000 ex­o­plan­ets have been de­tected but we don’t know much about their com­po­si­tion and na­ture,” said Tinetti. “By ob­serv­ing a large sam­ple of plan­ets, we hope to re­veal se­crets about their chem­istry, for­ma­tion and evolution.” — AFP

A handout artist’s im­pres­sion shows the K2-18b su­perEarth, the only ex­o­planet known to host both wa­ter and tem­per­a­tures that could sup­port life. — AFP

Newspapers in English

Newspapers from Kuwait

© PressReader. All rights reserved.