Structs help astros modelling

astros.cpp

// planetas.cpp
// juanfc 2012-06-24
//

#include <iostream>
#include <cmath>
using namespace std;

const float G = 6.6738410E-11; // N·m2/kg2

struct TTime {
    int year, month, day, hour, min, sec;
};

struct TAstro {
    string name;
    float mass;
    float pos[3];
    float radius;
    TTime t;
};

float gravForce(TAstro a, TAstro b);
void printAstro(TAstro a);

int main()
{
    TAstro earth = {"Earth", 5.9721986E24, {0, 0, 0}, 6378E3, {2012,11,26,15,00,00}};
    TAstro mars  = {"Mars",  6.491E23,     {0, 3.1924E11, 0}, 3397E3, {2012,11,26,15,00,00}};


    printAstro(earth);
    printAstro(mars);

    float force = gravForce(earth, mars);

    cout << "The force between " << earth.name << " and " << mars.name << " es: " <<
         force << " Newtons" << " = " << force/9.8 << " Kg" << endl;

// gravitational force | 3.956×10^15 N  (newtons)


    return 0;
}

float gravForce(TAstro a, TAstro b)
{
    float d2 =  pow(a.pos[0] - b.pos[0], 2) +
                pow(a.pos[1] - b.pos[1], 2) +
                pow(a.pos[2] - b.pos[2], 2);
    return (G*a.mass*b.mass)/d2;
}

void printAstro(TAstro a)
{
    cout << "Name:   " << a.name << endl;
    cout << "Mass:   " << a.mass << endl;
    cout << "Pos:   [" << a.pos[0] << ", " <<
                        a.pos[1] << ", " <<
                        a.pos[2] << "]" << endl;
    cout << "Radius: " << a.radius << endl;
    cout << "Time:   " <<
    a.t.year << "-" << a.t.month << "-" << a.t.day << "." <<
    a.t.hour << "." << a.t.min << "." << a.t.sec << endl;
}