哈葛爾沙丘場

哈葛爾沙丘場（Hagal）是火星北極高原下方一處沙丘場的非正式名稱^[1]^[2] ，其名字來源於弗蘭克·赫伯特小說《沙丘》中虛構的哈葛爾星球^[2]。它的中心坐標位於北緯78.0度、東經84度處，由帶東南向背風面的線形和圓形沙丘組成^[2]。它是火星勘測軌道飛行器上高分辨率成像科學設備相機在季節性探索^[2]的第三年（火星31年）^[3]，以每六周一次的速率進行成像的目標沙丘之一。由於該沙丘呈直線和圓形，具有點、槓的外觀，因此也被稱為「火星莫爾斯密碼」^[1]^[4]^[5]^[6]。

形成

雖然通常可從沙丘的走向和形狀獲得有關風向的信息，但由於哈葛爾沙丘形狀複雜，所以很難確定所形成的風向。在該沙丘場情況中，理論上認為可能是隕石撞擊在地面形成裝滿沙子的局部隕坑，減少了形成沙丘的沙子數量；反過來這又會影響當地的地形，導致風向發生變化^[1]^[4]。

美國宇航局關於火星摩爾斯電碼的視頻剪輯。

線形沙丘（橫槓）是通過垂直於沙丘線的雙向風產生出漏斗效應，引導沙子沿沙丘線性軸堆積而成；而當導致線性堆積的風被阻斷時，則就形成了圓形沙丘（圓點），圓形沙丘被歸類為「新月形沙丘」。然而，這兩種結構的確切形成機制仍不清楚，這也是高分辨率成像科學設備任務選擇該區域進行成像的原因^[4]。

高分辨率成像科學設備相機定位專家維羅妮卡·布雷（Veronica Bray）評論說，火星上的其他地方也有類似形狀的沙丘，但由於其地形的罕見特徵，哈葛爾沙丘場提供了更好的圖像。布雷還將沙丘的分布結構「莫爾斯碼」解碼為「NEE NED ZB 6TNN DEIBEDH SIEFI EBEEE SSIEI ESEE SEEE!!」^[7]^[8]。

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參考文獻

^ ^1.0 ^1.1 ^1.2 Jeffrey Kluger. Here's What Explains the 'Morse Code' on Mars. Time magazine. 12 July 2016 [2022-04-05]. （原始內容存檔於2021-11-26）.
^ ^2.0 ^2.1 ^2.2 ^2.3 C.J. Hansen; S. Byrne; G. Portyankina; M. Bourke; C. Dundas; A. McEwen; M. Mellon; A. Pommerol; N. Thomas. Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes (PDF). Icarus. 2013, (225): 881–897 [19 July 2017]. （原始內容存檔 (PDF)於2022-02-01）. Please see note at Table 1 page 883: Table 1 Sites imaged systematically by HiRISE in study year 3 (MY31) of seasonal campaign. The names are informal, some based on the sand dunes in the science fiction book Dune.
^ Colin M. Dundas; Shane Byrne; Alfred S. McEwen; Michael T. Mellon; Megan R. Kennedy; Ingrid J. Daubar; Lee Saper. HiRISE observations of new impact craters exposing Martian ground ice. Journal of Geophysical Research. 27 January 2014, 119 (1): 109. Bibcode:2014JGRE..119..109D. doi:10.1002/2013JE004482. Six sites were discovered in the northern summer of Mars Year 29 (MY29), seven in MY30, and seven in MY31. (MY refers to the Mars calendar of Clancy et al. [2000], and this notation will be used throughout this paper; years begin at LS = 0°, the beginning of northern spring. MY32 began on 31 July 2013.)
^ ^4.0 ^4.1 ^4.2 Martian Morse Code. NASA. 8 July 2016 [2022-04-05]. （原始內容存檔於2022-03-31）.
^ Martian Morse Code ESP_045334_2580. HiRISE. 29 June 2016 [2022-04-05]. （原始內容存檔於2021-10-22）.
^ Jessica F. Morse Code in Sand Dunes Found on Mars?. Nature World News. 12 July 2016 [2022-04-05]. （原始內容存檔於2020-01-06）. NASA calls the formation the "Martian Morse Code,"
^ Maddie Stone. There's a Secret Message Written Into the Sands of Mars. Gizmodo. 8 July 2016 [2022-04-05]. （原始內容存檔於2022-04-09）.
^ Doug Criss. Message from Mars? Morse code dunes found on red planet. CNN. 13 July 2016 [2022-04-05]. （原始內容存檔於2022-04-05）.

外部連結

Martian Morse Code by UAHiRISE on Youtube （頁面存檔備份，存於網際網路檔案館）

[Time_magazine-1] 1.0 ^1.1 ^1.2 Jeffrey Kluger. Here's What Explains the 'Morse Code' on Mars. Time magazine. 12 July 2016 [2022-04-05]. （原始內容存檔於2021-11-26）.

[Icarus-2] 2.0 ^2.1 ^2.2 ^2.3 C.J. Hansen; S. Byrne; G. Portyankina; M. Bourke; C. Dundas; A. McEwen; M. Mellon; A. Pommerol; N. Thomas. Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes (PDF). Icarus. 2013, (225): 881–897 [19 July 2017]. （原始內容存檔 (PDF)於2022-02-01）. Please see note at Table 1 page 883: Table 1 Sites imaged systematically by HiRISE in study year 3 (MY31) of seasonal campaign. The names are informal, some based on the sand dunes in the science fiction book Dune.

[JGR-3] Colin M. Dundas; Shane Byrne; Alfred S. McEwen; Michael T. Mellon; Megan R. Kennedy; Ingrid J. Daubar; Lee Saper. HiRISE observations of new impact craters exposing Martian ground ice. Journal of Geophysical Research. 27 January 2014, 119 (1): 109. Bibcode:2014JGRE..119..109D. doi:10.1002/2013JE004482. Six sites were discovered in the northern summer of Mars Year 29 (MY29), seven in MY30, and seven in MY31. (MY refers to the Mars calendar of Clancy et al. [2000], and this notation will be used throughout this paper; years begin at LS = 0°, the beginning of northern spring. MY32 began on 31 July 2013.)

[NASA-4] 4.0 ^4.1 ^4.2 Martian Morse Code. NASA. 8 July 2016 [2022-04-05]. （原始內容存檔於2022-03-31）.

[HiRISE-5] Martian Morse Code ESP_045334_2580. HiRISE. 29 June 2016 [2022-04-05]. （原始內容存檔於2021-10-22）.

[Nature_World_News-6] Jessica F. Morse Code in Sand Dunes Found on Mars?. Nature World News. 12 July 2016 [2022-04-05]. （原始內容存檔於2020-01-06）. NASA calls the formation the "Martian Morse Code,"

[Gizmodo-7] Maddie Stone. There's a Secret Message Written Into the Sands of Mars. Gizmodo. 8 July 2016 [2022-04-05]. （原始內容存檔於2022-04-09）.

[CNN-8] Doug Criss. Message from Mars? Morse code dunes found on red planet. CNN. 13 July 2016 [2022-04-05]. （原始內容存檔於2022-04-05）.

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