A big bright rock Options

[mpc]

I stumbled over an interesting rock in Isidis Planitia. Or maybe it's not interesting, please decide yourself. I have been crawling around the area a little bit and haven't found an object that would be similar to this one. There are rocks of about the same size and also rocks of the same brightness but the combination of either quality in a single object stood out to me.

The place where it sits has been imaged by HiRISE twice: ESP_013924_1915 (2009) and ESP_037356_1915 (2014). Click the image below to see an animated GIF compiled from cutouts of either HiRISE image. The scale is 1.0 (28 cm/pixel) which makes the rock's diameter to be 7-8 m.



I also looked up CTX images of that place and found three: P13_006171_1921_XN_12N269W (2007), B11_013924_1915_XN_11N269W (2009) and D04_028706_1917_XN_11N269W (2012). Click the image below for an animated composition. The scale is 1.0 (5.5 m/pixel) which is just enough for the rock to be visible to CTX.



The rock can be clearly made out from the 2009 and 2012 images, but not from the 2007 image. Do you think that's because of different lighting conditions in 2007? Or was it not there yet? I was also wondering what the rock was made of to be this bright.

Thanks,
Michael