<Li> The sample must have remained a closed system since the event being dated . Thus, there should have been no loss or gain of or Ar *, other than by radioactive decay of . Departures from this assumption are quite common, particularly in areas of complex geological history, but such departures can provide useful information that is of value in elucidating thermal histories . A deficiency of Ar in a sample of a known age can indicate a full or partial melt in the thermal history of the area . Reliability in the dating of a geological feature is increased by sampling disparate areas which have been subjected to slightly different thermal histories . </Li> <P> Both flame photometry and mass spectrometry are destructive tests, so particular care is needed to ensure that the aliquots used are truly representative of the sample . Ar--Ar dating is a similar technique which compares isotopic ratios from the same portion of the sample to avoid this problem . </P> <P> Due to the long half - life, the technique is most applicable for dating minerals and rocks more than 100,000 years old . For shorter timescales, it is unlikely that enough argon - 40 will have had time to accumulate in order to be accurately measurable . K--Ar dating was instrumental in the development of the geomagnetic polarity time scale . Although it finds the most utility in geological applications, it plays an important role in archaeology . One archeological application has been in bracketing the age of archeological deposits at Olduvai Gorge by dating lava flows above and below the deposits . It has also been indispensable in other early east African sites with a history of volcanic activity such as Hadar, Ethiopia . The K--Ar method continues to have utility in dating clay mineral diagenesis . Clay minerals are less than 2 micrometres thick and cannot easily be irradiated for Ar--Ar analysis because Ar recoils from the crystal lattice . </P> <P> In 2013 the K--Ar method was used by the Mars Curiosity rover to date a rock on the Martian surface, the first time a rock has been dated from its mineral ingredients while situated on another planet . </P>

What is a major advantage of k-ar dating over other forms of radiometric dating
find me the text answering this question