Free Astronomy Magazine July-August 2025 ARABIC VERSION

stantly released from the surface of oceans and seas up into the atmos- phere, but constitutes only about a billionth of its total mass. Depending on the altitude reached in the atmosphere and the amount of radiation from space, the life of DMS molecules can last from a few hourstoafewdaysbeforeultravi- olet rays and interactions with other gasesdestroythem.IftheEarthwere devoid of life, most likely there would be no trace of DMS in its at- mosphere. Given the speed with which its chemical bonds break, there would equally be no trace of DMS if it were not being constantly synthesized. Dimethylsulfideasa biosignature Dimethyl sulfide (CH 3 SCH 3 , or DMS) is a volatile organic compound of sulfur,producedprimarilyonEarth by the degradation of metabolites of phytoplankton and bacteria.DMShasacharacteristicunp leasant smell that can resemble brackish water, boiled broccoli, or rotten eggs.Onourplanet,DMSiscon- JULY-AUGUST2025 ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 5 ﻗﺪ ـﺔ رﻤﺎ ﺗﺸ ﮫ اﻟﻤﺼﻮرة ﻫﻨـﺎ ﻫـﻲ اﻟﻤﺴـﺌﻮﻟﺔ ﻋـﻦ ﺼـﻤﺔ ﺣﻴﻮ ﺗ ﻮن ﻣ ﻤﻮﻋﺎت اﻟﻌﻮاﻟﻖ اﻟﻨ ﺎﺗ ﺔ اﻟ ﺗﺴﻤﻰ ﺛﻨﺎﺋﻲﻣ ﺜﻴﻞ اﻟﻜ ﺘ ﺪ وﻫﻮ ﻏﺎزﺑﻴﻮﻟﻮﺟﻲ ر ﺗـﻢ اﻟﻜﺸـﻒ ﻋـﻦ آﺛـﺎرﻩ ﺴﻲواﻟ ـﻒ ﻓـﻲ ﺗﺤﻠﻴـﻞ ﻃ اﻟ ﻮﻛﺐ اﻟﻨ ﻤﻲ K2-18 b ﻓﻲﺟﺎﻣﻌﺔ ﺎﻣ ﺪج وﻓﻘًﺎ ﻟ ﺎﺣﺜ . [Getty] ﺛﻨﺎﺋﻲﻣ ﺜﻴﻞ اﻟﻜ ﺘ ﺪ ﻛﻌﻼﻣﺔﺣﻴﻮ ﺔ ﺛﻨـﺎﺋﻲ ﻣﻴﺜﻴـﻞ اﻟﻜﱪﻳﺘﻴـﺪ (CH3SCH3) أو اﺧﺘﺼ ـﺎرا ) DMC ( وﻫ ـﻮ ﻣﺮﻛ ـﺐ ﻋﻀ ـﻮي ﻣﺘﻄﺎﻳﺮ ﻣﻦ اﻟﻜﱪﻳﺖ ﻳﻨﺘﺞ ﺑﺸﻜﻞ أﺳﺎﳼﻋﲆ اﻷرض ﻋﻦ ﻃﺮﻳﻖ ﺗﺤﻠﻞ ﻣﺴﺘﻘﻠﺒﺎت اﻟﻌﻮ اﻟـﻖ اﻟﻨﺒﺎﺗﻴﺔ واﻟﺒﻜﺘ ﻳﺎ اﻟ ﺒﺤﺮﻳﺔ وﻫﻮ ﻳﻌﺘـﱪ ﻏـﺎز ﺣﻴﻮي ﻣﻬﻢ وﻟﻪ راﺋﺤﺔ ﻛﺮﻳﻬﺔ ﻣﻤﻴﺰة ﻳﻤﻜـﻦ أن ﺗﺸﺒﻪ ا ﻴـﺎه ﻗﻠﻴﻠـﺔ ا ﻠﻮﺣـﺔ أو اﻟـﱪوﻛﲇ ا ﺴﻠﻮق أو اﻟﺒﻴﺾ اﻟﻔﺎﺳﺪ ؟ ﻳ ﻨﺒﻌـﺚ ﺛﻨـﺎﺋﻲ ﻣﻴﺜﻴـﻞ اﻟﻜﱪﻳﺘﻴــﺪ ﰲ ﻛﻮﻛﺒﻨـﺎ ﺑﺎﺳﺘﻤﺮار ﻣﻦ ﺳﻄﺢ ا ﺤﻴﻄـﺎت واﻟﺒﺤـﺎر إﱃ اﻟﻐﻼف اﻟﺠﻮي وﻟﻜﻨﻬﺎ ﻻ ﺗﺸﻜﻞ ﺳﻮى واﺣـﺪ ﻣﻦ ا ﻠﻴﺎر ﻣﻦ ﻛﺘﻠﺘﻪ اﻟﻜﻠﻴ .ﺔ اﻋﺘﻤﺎد اً ﻋﲆ اﻻرﺗﻔﺎع اﻟﺬي ﻳﺘﻢ اﻟﻮﺻﻮل إﻟﻴـﻪ ﰲ اﻟﻐﻼف اﻟﺠﻮي وﻛﻤﻴﺔ اﻹﺷﻌﺎع اﻟﻘﺎدم ﻣـﻦ اﻟﻔﻀﺎء ﻳﻤﻜﻦ أن ﻳﺴﺘﻤﺮ ﻋﻤﺮ ﺟﺰﻳﺌﺎت ﺛﻨﺎﺋﻲ ﻣﻴﺜﻴﻞ اﻟﻜﱪﻳﺘﻴﺪ ﻣﻦ ﺑﻀـﻊ ﺳـﺎﻋﺎت إﱃ أﻳـﺎم ـــ ﻗﻠﻴﻠــﺔ ﻗﺒــﻞ أن ﺗــﺪﻣﺮﻫﺎ اﻷﺷــﻌﺔ ﻓــﻮق اﻟﺒﻨﻔﺴﺠﻴﺔ واﻟﺘﻔﺎﻋﻼت ﻣﻊ اﻟﻐﺎزات اﻷﺧـﺮى وﻟﻮ ﻛﺎﻧﺖ اﻷرضﺧﺎﻟﻴـﺔ ﻣـﻦ اﻟﺤﻴـﺎة ﻓﻌـﲆ اﻷرﺟﺢ ﻟﻦ ﻳﻜﻮن ﻫﻨﺎك أي أﺛﺮ ﻟ ﺜﻨﺎﺋﻲ ﻣﻴﺜﻴـﻞ اﻟﻜﱪﻳﺘﻴﺪ ﰲ ﻏﻼﻓﻬﺎ اﻟﺠﻮي . و ﻧﻈﺮاً ﻟﻠﴪﻋﺔ اﻟ ﺘـﻲ ﺗﺘﻔﻜـﻚ ﺑﻬـﺎ اﻟـﺮواﺑﻂ اﻟﻜﻴﻤﻴﺎﺋﻴﺔ ﻓﻠﻦ ﻳﻜﻮن ﻫﻨﺎك أﺛﺮ ﻟﻪ إذا ﻟﻢ ﻳـﺘﻢ ﺗﺼﻨﻴﻌﻪ ﺑﺎﺳﺘﻤﺮار . ﻳﻮﻟﻴﻮ - ﺃﻏﺴﻄﺲ 2 0 2 5