The more convenient a triangle is to make, the more likely it is the correct shape you have to form to generate part of the complete Vertex picture. Once a line is formed into part of a triangle ...

The vertex shader is used to transform the attributes of vertices (points of a triangle) such as color, texture, position and direction from the original color space to the display space.

To see the Mars Triangle, Space.com suggests looking east around 6:30 p.m. local time. Mars is the brightest point and currently the vertex of the triangle, with Castor and Pollux making up the base.