Revise Mars colonization phases and add images

Updated the phases of Mars colonization and added relevant images.

Author: mokun

content/docs/about/_index.md

@@ -7,34 +7,40 @@ menu:
     weight: 10
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-Robert Zubrin once proposed four phases in the economics of Mars colonization. Each represents a new progressive stage of increased human activities toward building a human civilization on Mars.				
-							
+{{< figure src="/images/colonizingmars2.jpg" caption="Terraforming Mars is not for faint of heart. Image credit: Stefan Morrell. Sources: Christopher McKay, NASA Ames Research Center; James Graham, University of Wisconsin–Madison; Robert Zubrin, Mars Society; Margarita Marinova, California Institute of Technology" >}}
+
+Robert Zubrin once proposed four distinct phases in colonizing Mars. 
+
+Each represents a new progressive stage of increased human activities toward building a human civilization on Mars.										
+
 {{< figure src="/images/marsyear135.gif" caption="Image from MarsOne" >}}
 
-## EXPLORATION
+## PHASE 1 : EXPLORATION
 
 Orbital survey of Mars, telescopic and robotic survey, precursor sample return, scientific investigations, human flyby/EVA/landing/return;  
 
 {{< figure src="/images/analysis.jpg" caption="Image credit: Mashable.com, 2013" >}}
 
 
-## BASE BUILDING
+## PHASE 2 : BASE BUILDING
 
 Semi-permanent laboratory/habitat modules, crew rotations, water/ice recovery, in-situ fuel production, outpost maintenance/sustainment;
 
 {{< figure src="/images/habcutout.jpg" caption="Cutaway of a proposed 4-person Habitat Module. Image: Ian Warpole, Scientific American" >}}
 
-## SETTLEMENT
+## PHASE 3 : SETTLEMENT
 
 Colony expansion, food and resources supply chain, terrestrial exploitation, economic viability, industrial production, infrastructure redundancy;     
 
 {{< figure src="/images/construction2.jpg" caption="Image from Outerplaces.com and Mars-One.com" >}}
 
-## TERRAFORMING
+## PHASE 4 : TERRAFORMING
 
 Altering global climate, large scale geo-engineering, permanently transforming human surface activities.  
 
-Currently, mars-sim focuses primarily in offering a simulation engine showcasing human activities in the aforementioned phase 1 and some phase 2 and a little bit of phase 3. Below are the five core features of mars-sim:								
+## CONCLUSION
 
-{{< figure src="/images/colonizingmars2.jpg" caption="Terraforming Mars is not for faint of heart. Image credit: Stefan Morrell. Sources: Christopher McKay, NASA Ames Research Center; James Graham, University of Wisconsin–Madison; Robert Zubrin, Mars Society; Margarita Marinova, California Institute of Technology" >}}
-	
+Currently, mars-sim focuses primarily in offering a simulation engine showcasing human activities. It depicts a little bit of phase 1 and is primarily about establishing phase 2 and moving onto phase 3. 
+
+Below are the five core features of mars-sim:
+