Targeting Planeswalkers

[Man of Steel]

Can Wallking Ballista and/or Ghirapur Aethergrid target Planeswalkers??

Thanks

[mistercakes]

http://gatherer.wizards.com/Pages/Card/Details.aspx?name=walking%20ballista

Card Text:
Walking Ballista enters the battlefield with X +1/+1 counters on it.
4: Put a +1/+1 counter on Walking Ballista.
Remove a +1/+1 counter from Walking Ballista: It deals 1 damage to any target.



Card Text:
Tap two untapped artifacts you control: Ghirapur Aether Grid deals 1 damage to any target.