In order to survive, you will have to get to a nearby asteroid ASAP and start digging it out with your hand-drill. Ores are all visible in Space Engineers through certain textures. In this case, on the very surface is a small deposit of Iron. It has a brownish, smooth texture to it.
Using your drill will destroy sections of asteroids and make small, floating ore nuggets appear in place of them.
Press (T) to pick them up and they'll be placed in your limited space inventory.
Finding certain minerals can be very difficult. For example, that tiny small iron spot we had on the surface of this asteroid ended up being a gigantic, inwards-going iron deposit.
The grey stuff outside on asteroids is all stone. You want to avoid picking up any of those "nuggets" as they are useless.
Holding (T) while drilling will make your job a whole lot easier as It will automatically pick up any ingots that happen to spawn at your cursor following the destruction of an asteroid section.
I recommend making a small tunnel before making an 360 expansion bubble as nuggets tend to not only bounce around but also drift off.
Just don't make too much of a complicated tunnel network. You'll need to find yourself out with regular intervals to supply your suit with power.
Power is drained faster by both using the jetpack (necessary for manouvering) and your hand-drill.
Simply hold (T) at the medstation to refill said power.