Martian Burial Site

Here is a photograph of a Dogs Cemetery at Molesworth in Huntingdon. Some of the dogs' names are visible. They include: Jinnie, Fitz, Viper, Joan and Mackie. In the case of the latter, Mackie's large headstone [front, left] bears the following description:
"In Memory of Mackie [Martian Wee MacGregor)
Died in India September 7, 1912
Aged 7 years
Clever and Affectionate, this little Scottie was a great companion and never failing delight to his Mistress who bitterly regrets him.
His place can never be filled"

Why does his headstone bear the word 'Martian?' What does this mean?