Free Astronomy Magazine November-December 2024 ARABIC VERSION

Mars’ water loss is linked to its distance from the Sun byNASA AnnJenkins5RayVillard stand how the atoms escape into space.” Clarkeandhisteamcombineddata from Hubble and MAVEN to meas- urethenumberandcurrentescape rate of the hydrogen atoms escap- ing into space. This information al- lowed them to extrapolate the es- cape rate backwards through time to understand the history of water on the Red Planet. Water molecules in the Martian at- mosphere are broken apart by sun- light into hydrogen and oxygen atoms. Specifically, the team meas- ured hydrogen and deuterium, which is a hydrogen atom with a neutroninitsnucleus.Thisneutron givesdeuteriumtwicethemassof rs was once a very wet planet as is evident in its surfacegeologicalfeatures. Scientistsknowthatoverthelast3 billion years, at least some water went deep underground, but what happenedtotherest?Now,NASA’s HubbleSpaceTelescopeandMAVEN (MarsAtmosphereandVolatileEvo- lution) mission are helping unlock that mystery. “There are only two places water can go. It can freeze into the ground, or the water molecule can breakintoatoms,andtheatomscan escape from the top of the atmos- phere into space,” explained study leader John Clarke of the Center for SpacePhysicsatBostonUniversityin Massachusetts. “To understand how much water there was and what happenedtoit,weneedtounder- hydrogen.Becauseitsmassishigher, deuterium escapes into space much more slowly than regular hydrogen. Over time, as more hydrogen waslost than deuterium, the ratio of deuterium to hydrogen built up in theatmosphere.Measuringthe ratio today gives scientists a clue to how much water was present during the warm, wet period on Mars. By studyinghowtheseatomscurrently ُﻌــــــــــﺪ اﻟﻤــــــــــﺮ ﺦ ﻋــــــــــﻦ اﻟﺸــــــــــــــــﻤ ﺲ ﺳــــــــــــــــ ﺐ ﻓﻘﺪاﻧﮫ ﻟﻠﻤ ﺎﻩ ﻧﻮﻓﻤﺒﺮ - ﺩﻳﺴﻤﺒﺮ 2 0 2 4 : ﻘﻠﻢ آن ﺟ ﻨﻜ و راي ﻓ ﻼرد و ﺎﻟﺔ ﻧﺎﺳﺎ ﻟﻘـﺪ ﻛﺎن ﻛﻮﻛﺐ ا ﺮﻳﺦ ﰲ ﻳـﻮم ﻣـﻦ اﻷﻳـﺎم ﺎً ﻛﻮﻛﺒ ﺎً رﻃﺒ ﻟﻠﻐﺎﻳﺔ ﻛﻤﺎ ﻳﺘﻀﺢ ﻣﻦ اﻟﺴﻤﺎت اﻟﺠﻴﻮﻟﻮﺟﻴﺔ ﻟﺴﻄﺤﻪ . ﻳﻌﻠﻢ اﻟﻌﻠﻤﺎء أﻧﻪ ﻋﲆ ﻣ ﺪار اﻟﺜﻼﺛﺔ ﻣﻠﻴﺎرات ﺳﻨﺔ ا ﺎﺿﻴﺔ اﺧﺘﻔـﺖ ﺑﻌﺾ ا ﻴﺎه ﻋﲆ اﻷﻗـﻞ ﰲ أﻋﻤـﺎق اﻟ ﻴ ﺎﺑﺴـﺔ وﻟﻜﻦ ﻣﺎذا ﺣﺪث ﻟﺒﻘﻴﺔ ا ﻴـﺎه ؟ اﻵن ﺗﺴـﺎﻋﺪ ﻣﻬﻤﺔ ﺗﻠﺴـﻜﻮب ﻫﺎﺑـﻞ اﻟﻔﻀـﺎﺋﻲ اﻟﺘـﺎﺑﻊ ﻟﻮﻛﺎﻟﺔ ﻧﺎﺳﺎ وﻣﻬﻤﺔ ﻣﺎﻓﻦ ﰲ ﺣﻞ ﻫﺬا اﻟﻠﻐﺰ . أوﺿﺢ ﺟﻮن ﻛﻼرك، ﻗﺎﺋﺪ اﻟﺪراﺳﺔ ﻣﻦ ﻣﺮﻛﺰ ﻓﻴﺰﻳــﺎء اﻟﻔﻀــﺎء ﺑﺠﺎﻣﻌــﺔ ﺑﻮﺳــﻄﻦ ﰲ ﻣﺎﺳﺎﺗﺸﻮﺳﺘﺲ، " ﻻ ﻳﻮﺟﺪ ﺳـﻮى ﻣﻜـﺎﻧ ﻓﻴﺰﻳــﺎء اﻟﻔﻀــﺎء ﺑﺠﺎﻣﻌــﺔ ﺑﻮﺳــﻄﻦ ﰲ ﻣﺎﺳﺎﺗﺸﻮﺳﺘﺲ، " ﻻ ﻳﻮﺟﺪ ﺳـﻮى ﻣﻜـﺎﻧ ﻳﻤﻜـﻦ أن ﻳـﺬﻫﺐ إﻟﻴﻬﻤـﺎ ا ـﺎء . ﻳﻤﻜـﻦ أن ﻳﺘﺠﻤﺪ ﰲ اﻷرض، أو ﻳﻤﻜ ﻦ ﻟﺠﺰيء ا ـﺎء أن ﻳﻨﻜﴪ إﱃ ذرات وﻳﻤﻜﻦ ﻟﻠـﺬرات أن ﺗﻬـﺮب ﻣﻦ أﻋﲆ اﻟﻐﻼف اﻟﺠ ﻮي إﱃ اﻟﻔﻀﺎء . ﻟﻔﻬـﻢ ﻛﻤﻴـ ﺔ ا ﻴـﺎه ا ﻮﺟـﻮدة وﻣـﺎذا ﺣـﺪث ﻟﻬـﺎ ﻧﺤﺘﺎج إﱃ ﻓﻬﻢ ﻛﻴﻔﻴـﺔ ﻫـﺮوب اﻟـﺬرات إﱃ اﻟﻔﻀـﺎء ." ﻟﻘــﺪ ﺟﻤ ـﻊ ﻛــﻼرك وﻓﺮﻳﻘــﻪ اﻟﺒﻴﺎﻧﺎت ﻣﻦ ﻫﺎﺑـﻞ وﻣـﺎﻓﻦ ﻟﻘﻴـﺎس ﻋـﺪد وﻣﻌﺪل ﻫﺮوب ذرات اﻟﻬﻴﺪروﺟ اﻟﺤﺎﻟﻴﺔ إﱃ وﻣﻌﺪل ﻫﺮوب ذرا ت اﻟﻬﻴﺪروﺟ اﻟﺤﺎﻟﻴﺔ إﱃ اﻟﻔﻀﺎء وﻗﺪ ﺳﻤﺤﺖ ﻟﻬﻢ ﻫـﺬه ا ﻌﻠﻮﻣـﺎت ﺑﺎﺳﺘﻘﺮاء ﻣﻌﺪل اﻟﻬﺮوب ﻋﱪ اﻟـﺰﻣﻦ ﻟﻔﻬـﻢ ﺗﺎرﻳﺦ ا ﺎء ﻋﲆ اﻟ ﻜﻮﻛﺐ اﻷﺣﻤﺮ . ﺗﺘﻔﻜـﻚ ﺟﺰﻳﺌـﺎت ا ـﺎء ﰲ اﻟﻐـﻼف اﻟﺠـﻮي ﻟﻠﻤ ـﺮﻳﺦ ﺑﻔﻌ ـﻞ ﺿـﻮء اﻟﺸ ـﻤﺲ إﱃ ذرات ﻫﻴﺪروﺟ وأﻛﺴﺠ وﻋﲆ وﺟـﻪ اﻟﺘﺤﺪﻳـﺪ ﻗ ــﺎم اﻟﻔﺮﻳ ــﻖ ﺑﻘﻴ ــﺎس اﻟﻬﻴ ــﺪروﺟ واﻟﺪﻳﻮﺗ ﻳﻮم، وﻫﻮ ذرة ﻫﻴ ﺪروﺟ ﺗﺤﺘﻮي ﻧﻮاﺗﻬﺎ ﻋﲆ ﻧﻴﻮﺗﺮون وﻳﻌﻄﻲ ﻫﺬا اﻟﻨﻴﻮﺗﺮون اﻟﺪﻳﻮﺗ ﻳﻮم ﺿﻌﻒ ﻛﺘﻠﺔ اﻟﻬﻴﺪروﺟ . وﻷن ﻛﺘﻠﺘﻪ أﻋﲆ ﻓﺈن اﻟﺪﻳﻮﺗ ﻳﻮم ﻳﻬـﺮب إﱃ اﻟﻔﻀــﺎء ﺑﺸــﻜﻞ أﺑﻄــﺄ ﺑﻜﺜــ ﻣﻘﺎرﻧــﺔ ﺑ ﺎﻟﻬﻴﺪروﺟ اﻟﻌﺎدي ﺑﻤـﺮور اﻟﻮﻗـﺖ وﻣـﻊ ﻓﻘ ـﺪ ا ﺰﻳــﺪ ﻣ ـﻦ اﻟﻬﻴــﺪروﺟ ﻣﻘﺎرﻧــﺔ ﺑﺎﻟـﺪﻳﻮﺗ ﻳﻮم ﻓـﺈن ﻧﺴـﺒﺔ اﻟـﺪﻳﻮﺗ ﻳﻮم إﱃ اﻟ ﻬﻴــﺪروﺟ ﺗ ـﱰاﻛﻢ ﰲ اﻟﻐ ـﻼف اﻟﺠ ـﻮي وﻳﻌﻄﻲ ﻗﻴﺎس اﻟﻨﺴﺒﺔ اﻟﻴﻮم ﻟﻠﻌﻠﻤﺎء ﻓﻜـﺮة ﻋﻦ ﻛﻤﻴﺔ ا ﺎء اﻟﺘﻲ ﻛﺎﻧﺖ ﻣﻮﺟـﻮدة ﺧـﻼل اﻟﻔﱰة اﻟﺪاﻓﺌﺔ اﻟﺮﻃﺒﺔ ﻋـﲆ ﻛﻮﻛـﺐ ا ـﺮﻳﺦ وﻣﻦ ﺧﻼ ل دراﺳﺔ ﻛﻴﻔﻴـﺔ ﻫـﺮوب اﻟـﺬرات ﺎً ﺣﺎﻟﻴـ ﻳﻤﻜـﻦ ﻟﻠﻌﻠﻤـﺎء اﻟﺘﻮﺻـﻞ اﱃ ﻓﻬـﻢ اﻟﻌﻤﻠﻴﺎت اﻟﺘﻲ ﺣﺪدت ﻣﻌﺪﻻت اﻟﻬﺮوب ﻋـﲆ ﻣﺪى اﻷرﺑﻌﺔ ﻣﻠﻴﺎرات ﺳﻨﺔ ا ﺎﺿﻴﺔ وﺑﺎﻟﺘﺎﱄ اﺳﺘﻘﺮاء ا ﺎﴈ .